Iran and Russia have threatened to hit back if the US follows up on its air strike in Syria last week, ramping up tensions in the Middle East.

It comes after Foreign Secretary Boris Johnson cancelled a trip to Moscow and prepared a new diplomatic offensive against Russia.

He is also set to urge the Russians to pull their forces out, something which would involve a major loss of face for President Putin.

Eighty-nine people, including 33 children, died on Tuesday after a nerve agent was used in an attack on the rebel-held town of Khan Sheikhoun in northern Syria.

Syrian Armed Forces chief of staff Ali Abdullah Ayyoub (centre, left) visited the al-Shayrat airfield near Homs to inspect the damage caused by 59 US cruise missiles

Abdul-Hamid Alyousef holds his children, Ahmad and Aya, who died when a nerve agent was released in their home town of Khan Sheikhoun

The Assad regime has denied it was responsible and the Russians have claimed it was a 'false flag' incident carried out by jihadists who want to stir up tensions between Russia and the US.

President Trump infuriated Moscow when he authorised an airstrike on a Syrian air base on Friday, which killed at least six people.

British Defence Secretary Sir Michael Fallon said today it was the 'right call' for the Americans to bomb the air base as retribiution for a 'barbaric, immoral and illegal' act by Syrian President Bashar al-Assad, who he described as a Russian 'proxy'.

But in a joint statement the Russian and Iranians said: 'We will respond to any aggression'.

The Sun reported that a joint command centre in Syria said: 'What America waged in an aggression on Syria is a crossing of red lines. From now on we will respond with force to any aggressor or any breach of red lines from whoever it is and America knows our ability to respond well.'

The nerve agent attack happened in Khan Sheikhoun, in rebel-held territory and the US fired missiles at al-Shayrat airfield in response

Iranian President Hassan Rouhani earlier condemned 'flagrant US aggression on Syria' following the Tomahawk strike on al-Shayrat.

While Russia's support for the Assad regime dates back to the 1970s and 80s when Bashar's father, Hafez, was a stalwart supporter of the Soviet Union and an implacable enemy of Israel, Iran's support is based on religion.

Assad is from the Alawite minority and has long nursed fears of a rebellion by the Sunni majority and has welcomed the support of Iran, an overwhelmingly Shia Muslim country which also has reason to fear Sunnis.

Boris Johnson has pulled out of a visit to Moscow in the wake of the Syrian chemical weapons attack saying 'we deplore Russia's continued defence of the Assad regime'

Boris Johnson, who was due to visit Russia tomorrow for talks with counterpart Sergey Lavrov, said yesterday: 'We deplore Russia's continued defence of the Assad regime'.

He called off the visit at the last minute after a midnight phone call with US Secretary of State, Rex Tillerson, which led to accusations by Russia that Britain had no independent foreign policy.

Lavrov spoke to Tillerson last night and he reportedly told the American 'that an attack on a country whose government is fighting against terrorism is only playing into extremists' hands'.

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Volunteers from the Syrian Civil Defence, also known as the White Helmets, tried to extract survivors from the rubble following reported air-strikes on the rebel-held town of Saqba

Mr Johnson said: 'We deplore Russia's continued defence of the Assad regime even after the chemical weapons attack on innocent civilians,' he said.

'My priority is now to continue contact with the US and others in the run up to the G7 meeting on 10-11 April.'

Mr Johnson then called on Russia to do 'everything possible to bring about a political settlement in Syria and work with the rest of the international community to ensure that the shocking events of the last week are never repeated'.

But Alex Salmond, the SNP's foreign affairs spokesman, said Johnson's move made him look him 'some sort of Mini Me' who cannot be trusted to hold his own talks withLavrov.

Salmond said : 'Boris Johnson just looks daft. What is the argument for not going ahead with a visit? Rex Tillerson is going on Wednesday so it can't be that we have moved to a Cold War position of no talking whatsoever.

'The idea the Foreign Secretary can't be trusted because he might pursue his own line or have an independent thought or crossover what the Americans are going to say just makes him look like some sort of Mini Me to the United States of America.'

But the Sunday Telegraph claims Johnson is trying to persuade Tillerson to move back to the original plan for regime change in Damascus.

Johnson's visit would have been the first visit by a UK foreign secretary in more than five years.

It comes as Britain gave full backing to the dramatic US missile strike on a Syrian air base in response to Bashar al-Assad's 'barbaric' chemical attack - with Theresa May having given her blessing to Donald Trump before it happened.

Mr Johnson attacked the Kremlin and said he would instead focus on building support with allies to secure a ceasefire in war-torn Syria

People inspect the Great Mosque, damaged during the Assad regime's airstrike, in Arbin town in Damascus, Syria

A U.S. Navy image shows the USS Ross (DDG 71) firing a tomahawk land attack missile at the Syrian air base



