DAMASCUS: A massive bomb blast rocked the heart of Damascus on Wednesday as pressure mounted on the regime, with the world’s largest pan-Islamic bloc poised to suspend Syria over the unrelenting violence.

The United States also accused Iran of setting up a pro-regime militia in Syria as Washington increasingly ties the conflict that is now in its 18th month to interference by long-time foe Tehran.

The Rebel Free Syrian Army claimed it was behind the bomb attack which it said targeted a military meeting taking place near the hotel used by the UN observer mission in Syria.

“There was a huge explosion and a fireball, and soldiers were thrown to the ground by the blast,” a military officer told AFP at the scene, adding that five people suffered burns or shrapnel wounds.

Damascus has been hit by several bomb blasts, including an attack last month that killed four of President Bashar al-Assad’s top security chiefs and was also claimed by the FSA.

Meanwhile, the Organisation of Islamic Cooperation, which represents 1.5 billion Muslims worldwide, was poised to suspend Syria at an emergency summit Wednesday in a move opposed by Iran, a staunch ally of Assad’s increasingly embattled regime.

The move by the OIC is aimed at further isolating Assad’s regime over a conflict that activists say has now claimed over 23,000 lives and has sent hundreds of thousands fleeing, but its effect is seen as largely symbolic.

Syria was suspended from the Arab League last year over its crackdown on the Arab Spring-inspired uprising that Assad has characterised as a plot by Western and rival Sunni powers to overthrow his Alawite-led regime.

A final draft statement says Syria should be suspended over “the obstinacy of the Syrian authorities in following the military option” and the failure of a peace plan brokered by former international envoy Kofi Annan.

It demands that Assad’s regime “immediately end all acts of violence” while defending Syria’s “unity, sovereignty, independence and territorial integrity.” Tensions have been simmering for months between Sunni-led Saudi Arabia and Shia-dominated Iran as Syria has emerged as another arena for the longtime rivalry between the two regional heavyweights.

Iran accused of ‘training militia within Syria’

Iran’s archfoe the United States accused Tehran Tuesday of setting up a militia in Syria and urged it to stay out of the conflict.

“It is obvious that Iran has been playing a larger role in Syria in many ways,” US Defence Secretary Leon Panetta said at a press conference.

He said the United States has evidence that Iran’s elite Revolutionary Guards were “trying to develop, trying to train a militia within Syria to be able to fight on behalf of the regime.”

“We are seeing a growing presence by Iran and that is of deep concern to us. We do not think that Iran ought to play that role at this moment in time, that’s dangerous... It’s adding to the killing that’s going on in Syria.” Further undermining the regime, Syria’s former prime minister, the highest profile government figure to defect, said Tuesday that the power structure was disintegrating.

“The Syrian regime only controls 30 per cent of Syria’s territory. It has collapsed militarily, economically and morally,” Riad Hijab told a news conference in Amman.

The United States, which has imposed a raft of tough sanctions to try to force Assad’s departure, reacted by lifting an asset freeze imposed on Hijab in a move it said was aimed at encouraging similar defections.

Western policymakers hope a wave of defections will bring the collapse of the autocratic government, ending a conflict that seems to be in stalemate with the international community deeply divided over what action to take.

Traditional Syria ally China’s top state newspaper accused Western powers of hampering efforts to end the conflict, as a senior Damascus envoy visited Beijing for talks with political leaders.

China and Russia have repeatedly used their vetoes to scuttle UN Security Council resolutions aimed at tackling the violence, putting them at loggerheads with fellow permanent members the United States, Britain and France.

“Some Western countries have never given up the goal of ‘regime change’ in Syria and constantly reinforced their support for the anti-government forces,” the People’s Daily said.

On the ground, activists reported heavy shelling in several rebel-held districts of the northern hub of Aleppo, seen as pivotal to the outcome of the rebellion.

Government forces also stormed several districts of Damascus in the third day of security raids in the capital.

The unrelenting violence has raised international concerns about the deteriorating humanitarian situation with over one million people displaced inside Syria and at least another 157,600 fleeing to neighbouring countries.