Here is a summary of what happened on a day when UK-Iranian relations plummeted further:

• Dozens of Iranian protesters forced their way into the British embassy in Tehran, tearing down the Union flag and throwing documents from the windows. They also pulled down a picture of the Queen and burnt an embassy vehicle, as well as US, Israeli and UK flags. The protesters said they wanted to shut down the embassy. Protesters also targeted Gholhak Gardens, a British diplomatic compound in north Tehran that has been a source of contention between Iranian and UK officials over its ownership. Both of the protests have now ended.

• The UK foreign secretary, William Hague, said he held the Iranian government responsible for failing to protect the embassy, despite Tehran's expressions of regret for today's events. The foreign office advised British nationals in Iran to stay indoors and keep a low profile after the attacks. The Iranian foreign ministry said it regretted the events and was committed to the safety of diplomats on its soil but Hague said it "remains a very serious failure by the Iranian government".

• The semi-official Fars news agency said six UK embassy staff were rescued by police after being held hostage by the protesters who it described as "self-motivated university students". The UK foreign office would not comment directly but Hague said that all staff had been accounted for.

• Clashes between police and protesters were reported at the UK embassy. One protester was in a critical condition, according to Fars. It said several protesters and police officers were injured. Police used teargas to try to disperse protesters. Some were reportedly arrested at Gholhak Gardens.

The UK's foreign secretary, William Hague (pictured left), has issued a strong statement on Iran. He said all embassy staff are accounted for but his anger has clearly not been mollified by Iran's expression of regret for today's events:

"This afternoon our two Embassy compounds in Tehran were stormed by several hundred people, putting the safety of our diplomats and their families at risk and causing extensive damage to our property. The United Kingdom takes this irresponsible action extremely seriously. It amounts to a grave breach of the Vienna Convention which requires the protection of diplomats and diplomatic premises under all circumstances. We hold the Iranian government responsible for its failure to take adequate measures to protect our embassy, as it is required to do. I spoke to the Iranian foreign minister this afternoon, to protest in the strongest terms about these events and to demand immediate steps to ensure the safety of our staff and of both Embassy compounds. While he said that he was sorry for what had happened and that action would be taken in response, this remains a very serious failure by the Iranian government. The Iranian charge d'affaires in London has been summoned to the Foreign Office this afternoon and the prime minister has chaired a meeting of Cobra. The safety of our staff is our utmost priority. On our latest information it now appears that all our staff and their dependants are accounted for. We are urgently establishing the whereabouts of our locally engaged security staff to ensure their wellbeing. All other locally engaged staff had been instructed not to attend the embassy today because of the likelihood of demonstrations. We warn British nationals against all but essential travel to Iran, and we advise the small number that are in Iran to stay indoors and to await further advice. We have made clear to the Iranian government that they must take immediate steps to ensure the safety of UK personnel; to ensure that property taken from the Embassy compounds is returned; and to secure the compounds with immediate effect. Clearly there will be other, further, and serious consequences. I will make a Statement updating Parliament on this tomorrow."

Tehran police chief, Hossein Sajedinia, has confirmed to the semi-official Mehr news agency that both the British embassy and its separate compound in the north of the capital, known as Gholhak gardens, have been evacuated.

The Iranian Students' News Agency, ISNA, says that protesters have also left the site of the second demonstration, Gholhak Gardens, a British diplomatic compound in north Tehran.

The protest at the embassy has ended and the building has been vacated by the protesters after they were given an ultimatum by the deputy commander of the Iranian police, according to the semi-official Fars news agency.

The Fars news agency (Farsi site) reports that Iranian protesters found pictures of the late Shah, Mohammad Reza Pahlavi (pictured left), who was overthrown in the 1979 Iranian revolution, among the documents confiscated at the British embassy.

Accompanying the article is a picture of the Shah and Queen Elizabeth said to have been seized from the embassy.

Some more on the expression of regret at today's events by the Iranian foreign ministry. The students' news agency ISNA quoted the Iranian government as saying:



The foreign ministry regrets the protests that led to some unacceptable behaviours ... We respect and we are committed to international regulations on the immunity and safety of diplomats and diplomatic places.

The semi-official Fars news agency says that one protester at the embassy compound is reportedly in a critical condition and a number of protesters and police officers wounded after clashes between the police and those who stormed the embassy grounds. Police fired teargas during the clashes.

Fars makes a point of saying the protesters were "self-motivated", thereby seeking to distance them from the Tehran regime.

It reports that some of the protesters have been arrested and that the Tehran police chief has told Fars they will be prosecuted. He also said an investigation is being conducted into the British embassy raid.

The chargé d'affaires of Iran's embassy in London has been summoned to the British foreign office, a source has told the Guardian.

Just breaking on Reuters - Iran's foreign ministry has said in a statement that it regrets the attack on the British Embassy in Tehran and is committed to diplomats' safety.

The official news agency IRNA says protesters staging a sit-in outside the British diplomatic compound in Gholhak garden are saying they will only leave on the orders of Ayatollah Ali Khamenei. It also has more on the secret documents supposedly seized by the protesters (see 2.49pm GMT / 9.49am EST).

Speaking to IRNA, one of the students said the protestors are studying the documents seized from the garden to get information on the UK's role in assassination of Iranian nuclear scientist Majid Shahriari. He added that having found the documents, the students hoped to prove the UK's role in assassination of important personalities and elite of the country.

The French foreign minister, Alain Juppe (left), has joined the condemnation of the attakc on the UK embassy. He said:

"France holds the Iranian authorities responsible for the integrity of all diplomatic missions in Tehran. Once more, the Iranian regime has shown what little consideration it has for international law. France denounces this flagrant and outrageous violation of the Vienna Convention."

Here is some more video footage from the demonstration at the embassy:

An unnamed protester, shown speaking on al-Jazeera, said:



We are here to close the UK embassy forever as this place is like the US embassy a centre for spying and should be shut down.

This Googlemap shows the location of the UK embassy in Tehran and of the British diplomatic compound in Gholhak Garden



View Iran attack on UK embassy/diplomatic compound in a larger map

The diplomatic compound is the point at the top of the map and the embassy is the point towards the bottom.

Reuters has this update (it should be stressed that the UK is not commenting on any of the reports about its staff other than to say that their safety is "paramount" to it, so they should be treated with caution):

Iranian police on Tuesday secured the release of six employees of the British embassy compound in northern Tehran who had been taken hostage by hardline students earlier in the day, the semi-official Fars news agency reported.

"Police freed the six people working for the British embassy in Gholhak garden," Fars said.

Gholhak Garden is where the British diplomatic compound is.

The Iranian Labour news agency has a gallery, which shows clearly some of the banners protesters are holding. They include:

"BBC don't lie" [presumably an exhortation rather than a statement] "English government are real terrorists" "We will answer threats with threats"

My colleague, Peter Walker, writes on the tumultuous history of the Tehran embassy:

The current Tehran embassy compound, in place for 135 years, has had a tumultuous existence, told in full on the Foreign Office website.

The building work alone – which took five years – was complicated by the architect's decision to transport the roof and other materials, such as glass, from the UK. Part of the roof was lost at sea in 1871, and two caravans of 367 camels transporting other materials were variously robbed by bandits and held to ransom by excise officials. Finally, a ship carrying glass and joinery caught fire at the port city of Bushehr. The building was finished in June 1876. In 1906, the embassy played a key role in the uprising which led to the establishment of a parliament in Iran, when well over 10,000 Tehran people took refuge in the compound. The foreign office history notes that Churchill, Stalin and Roosevelt met in Tehran for the first time to discuss the progress of the war and the future of Europe, even though the bulk of the meetings were at the Soviet embassy. With relations deteriorating following Iran's Islamic revolution in 1979, the embassy was emptied of all staff from 1987 to 1990, barring a month-long upturn in ties in 1989, just before Ayatollah Khomeini's fatwa against Salman Rushdie. Since 1999, Iran and the UK have exchanged ambassadors, rather than the lower-grade head of mission.

/ 10.46am EST The official Iranian IRNA news agency reports that around 50 students managed to enter the embassy but that police used water canon to try to stop others entering.

It adds:

The students are chanting "God is the Greatest", "Down with the UK," "Down with the US," and "Down with Israel."

@samy110, who tweets regularly about Iran, says it is not Iranian students responsible for the attack.

Those who attacked the British embassy in Tehran are thugs FYI Iranian students R either expelled from Uni or in prisons! #iranelection

The events in Tehran are already causing concerns on the oil markets. Energy strategist and economist Robin Mills tweets:

Embassy storming sends oil price up $2 per barrel, gaining Iran ~$5

million per day extra revenues

Here's an update from a spokesman at the UK foreign office:

Senior officials have spoken to the Iranian charge in London to urge the Iranian authorities to act with utmost urgency to ensure the situation is brought under control and to protect our diplomatic compound, as they are obliged to do under international law. This is a fluid situation and details are still emerging. We have updated our travel advice to reflect today's incident and now advise British nationals in Iran to stay indoors, keep a low profile and await further advice.

The Guardian's diplomatic editor, Julian Borger, writes that today's attack comes amid a background of - sometimes deadly - wrangling over Iran's nuclear programme:

Today is the first anniversary of the assassination of a senior Iranian nuclear scientist Majid Shahriari, seen by Tehran as a martyr to the Iranian nuclear cause. A number of the demonstrators are carrying images of the murdered scientist, who was said by the Tehran government to be in charge of an unspecified 'major project' within the country's Atomic Energy Organisation (IAEO). Shahriari was killed by a hit-team on motorcycles, who drove up to the door of his car and stuck a bomb on it, detonating it as they drove away. A simultaneous and identical attack was carried out on another senior scienist,

Fereidoun Abbasi Davani, who survived and a few months later was promoted to head of the IAEO. Iran has blamed Mossad for allegedly carrying out an assassination campaign against its scientists, but there is a widespread conviction in Tehran that Britain ultimately pulls the strings in plots against Iran. So this is very much part of the Iranian push back against the diplomatic and economic pressure on Tehran following this month's International Atomic Energy Agency (IAEA) report on the Iranian nuclear programme, reporting that there was 'credible' evidence that Iran had experimented with a nuclear warhead design and might still be. In the wake of the report, the UK was the first to take punitive action, cutting off dealings with Iran's central bank. Hence, the call from the Iranian parliament, the Majlis, last week to downgrade diplomatic relations with London. It is also very significant that some of the basiji, paramilitary youths, at the embassy, are carrying the picture of Qassem Suleimani, the head of the Quds Force of the Revolutionary Guard corps, which carries out external operations. This is a man who is clearly cultivating something of a personality cult around himself. He once wrote to General David Petraeus, then commanding coalition forces in Iraq, telling him if he wanted to talk about Iranian foreign policy he should talk exclusively to Suleimani. The Americans blame Suleimani for masterminding the bizarre alleged plot, uncovered last month, to blow up the Saudi ambassador to the US in a Washington restaurant. Many diplomats and observers believe he is a growing, radical force emerging amid the constant power struggle in Tehran.

The Guardian has a gallery of pictures from the attack on the embassy.

This is one of the images featured:

Meanwhile, the official Iranian IRNA news agency says the gate of Gholhak Gardens, a British diplomatic compound in north Tehran that has been a source of contention between Iranian and UK officials over its ownership, has been closed by security forces but the protesting students are continuing a sit-in. It reports the number of special security guards deployed there is "growing gradually".

Tabnak, a conservative website close to the former revolutionary guards commander, Mohsen Rezaei, claims the protesters have confiscated secret and spy documents from British embassy compound.

This YouTube video shows a large crowd at the embassy, chanting and waving flags and placards.

One man holds a Union flag with a skull and crossbones on it, others can be seen trying to break open the chain on the embassy's gates. At one point a man holds up a picture of the Queen, presumably taken from inside the embassy.

Dozens of Iranian protesters have forced their way into the British embassy in Tehran, tearing down the Union flag and throwing documents from the windows.

The Guardian's Saeed Kamali Dehghan writes: