It was a message, of course: the two bombs only metres from the Iranian embassy, the Iranian cultural attaché dead, the explosion heard across Beirut and all the vile detritus of the event; the leg under the broken balcony, the bits of teeth, the jaw with beard attached, the blood swamping the road.

At least 22 others were slaughtered. But how could you tell amid this horror? This was Shia Muslim territory in Beirut and the burning cars and smashed buildings of Jnah in south Beirut were quickly surrounded by uniformed Hezbollah militiamen and young men waving silver pistols.

A suicide bomber, we were told. There was another story. A small bomb to lure people into the street and then a massive car bomb to cut them down. Then one of the black-uniformed men said he believed a suicide bomber had set off the first, smaller bomb. Iranian embassy guards had tried to prevent the second blast – which tore the embassy gate from its hinges. At least 160 people were wounded in the two explosions.

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In the days of Twitter, who can trust a self-proclaimed al-Qa’ida outfit called the Abdullah Azzam brigades, which claimed the bombings and told Hezbollah to leave Syria? But could there be a more obvious target for those who curse Hezbollah’s military support for Bashar al-Assad in Damascus? Could there be a more ruthless way of hitting at the Shias of Lebanon than to go for the jugular and set off bombs so close to the embassy of a country which has sent its own Shia fighters to Syria? Offices of pro-Syrian television stations stand – or did stand – around the street. Only a week ago, Sayed Hassan Nasrallah, Hezbollah’s leader, warned that Lebanon was heading for a grave crisis. He was right.

Who could forget amid the burning cars and shoes and remnants of flesh that 66 Lebanese have been killed in the bombing of Shia and Sunni targets here in recent weeks. Now the figure is nearer 90. There is no government in Lebanon and the Lebanese army remains the only state institution functioning – apart from the central bank – and after the bombings Lebanese troops were outnumbered amid the smoke and rubble by the scores of Hezbollah men. Were the Hezbollah now the army of Lebanon? Or are they – as their Sunni Muslim opponents would say – now the army of Syria?

It is difficult to underestimate the seriousness of these sectarian bloodbaths. In the city of Tripoli, Sunnis have been blaming the Shia Hezbollah and the Syrian Alawites for bombs that killed 47 worshippers at two mosques in the city. Today, it was the Shia’s turn. They blamed the Saudis – who are trying, not very successfully, to overthrow Assad – and they blamed Saudi Arabia’s Gulf allies. The Syrian National Socialist Party’s former leader Fayed Shakr – a Shia from the Bekaa Valley – turned up to blame the Lebanese Christian leader Samir Geagea and the Sunni ex-prime minister Saad Hariri’s Future Party.

Interestingly and rather oddly, the Iranian ambassador, Ghazanfar Rokanabadi, who confirmed the death of his cultural attaché, Sheikh Ibrahim al-Ansari – a diplomat who had only been in Lebanon for a month – blamed the “Zionist regime” for the bombings, although he did not explain how Israel could be involved. There were rumours that Iranian embassy guards, most of whom are members of Hezbollah, were also killed.

The embassy is well-defended and looks more like a fortress than a diplomatic compound, although diplomats do live there. Nor is this any ordinary embassy. Over the years, I’ve seen a few well-known rogues pass through its portals – I collect my Iranian visas there – and if US embassies contain their share of spies, you can bet that the Iranian embassy in Beirut has some of their own intelligence men among its 28 staff.

The black flags of Ashura were still flying after the bombings in the streets around the embassy, marking the commemoration of the martyrdom of Hussein, grandson of the Prophet, whose sister Zeinab is also revered by Shias and is buried in Damascus. The Hezbollah have, for months, been protecting her shrine there.

“This is an attack on Zeinab,” a young man shrieked. And there’s the problem. The political divisions in Lebanon have become synonymous with the country’s religious divisions. If they become identical, then the danger is great indeed.

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Profile: Abdullah Azzam Brigades

Known to be active in Lebanon and the Arabian Peninsula, the Abdullah Azzam Brigades (AAB) has been linked to al-Qa’ida and is designated a Foreign Terrorist Organisation by the US State Department.

Founded in 2009, the group promotes itself as a protector of Sunni Muslims, and has spoken out against Hezbollah’s domination of Lebanon. The group claimed responsibility for the attacks, according to a statement posted on the Twitter account of Sirajuddin Zurayqat, an AAB spokesman, and a militant website.

It also said the group would continue such attacks until Hezbollah withdraws its forces from Syria.

One of AAB’s senior leaders is Saleh al-Qarawi, a Saudi Arabian citizen who is on the list of global terrorists subject to US sanctions. Interpol has issued an Orange notice for him.

Qarawi is believed to have fought against US forces in Fallujah, Iraq. According to the US State Department, while there, he worked with Abu Musab al-Zarqawi, the former head of al-Qa’ida in Iraq, who was responsible for the beheading of the kidnapped British engineer Ken Bigley in 2004.

The AAB has in the past claimed responsibility for rocket attacks into northern Israel, the 2010 bombing of a Japanese oil tanker in the Persian Gulf, and a 2005 rocket attack that narrowly missed a US amphibious ship docked at Jordan’s Aqaba Red Sea resort.