Hopes for peace shattered as scores are killed in twin Damascus blasts

At least 55 killed and hundreds injured as rush-hour explosions rock Syrian capital

Two suicide bombs exploded in Damascus yesterday, killing at least 55 people and wounding hundreds more in the single worst atrocity since the start of the Syrian uprising against President Bashar al-Assad's rule last year.

The massive rush-hour car bombings, which targeted a notorious branch of the Syrian secret police, sparked a round of claims and counter-claims, with the government blaming "terrorists" and the opposition accusing the regime for the devastating attack.

The explosions also cast a dark shadow over the UN peace mission to staunch the bloodshed across Syria. As the sheer scale of the destruction began to emerge, opposition leaders declared that the plan conceived by the UN-Arab league envoy, Kofi Annan, had failed. "We expect Kofi Annan to say that his plan has hit a dead end," said Samir Nashar, a member of the Syrian National Council. Mr Annan condemned the attacks as "abhorrent".

The explosions, which happened almost simultaneously, hit the southern al-Qazzaz district at around 8am. Moments after the blast an enormous mushroom cloud could be seen billowing hundreds of feet into the sky. One local likened it to the aftermath of a nuclear explosion. Professor Mohammad Borjia, a microbiologist who lives a mile away from the blast site, told The Independent that the bomb sprayed shards of metal and debris onto the roof of his apartment. "My friend lives in the al-Mazza district 10 miles away," said Dr Borjia, "and he thought the bomb had exploded near him."

Syria's state news agency published gruesome pictures of disembodied torsos and charred bodies hanging from incinerated cars. The cabin of one lorry close to the explosion had melted in the heat of the blast, while elsewhere panicked survivors were pictured running past dead bodies littering the asphalt.

The attacks happened close to the Palestine Branch Military Intelligence centre, one of the most feared departments of Syria's secret police. Although state television blamed "terrorists", nobody had claimed responsibility for the blasts last night. Previous government accusations against terrorists have been scotched by opposition activists, many of whom point the finger of blame at the Syrian regime. Opponents of the regime say its supporters have orchestrated a string of attacks to shore up wavering support among Syrians, a claim that was repeated yesterday.

But analysts are increasingly doubtful as to whether such claims stack up. Although it did not make any claims yesterday, a group linked to al-Qa'ida has said it was behind some of the explosions which have rocked Syria since December. "It beggars belief to imagine that this was the work of the security forces," said Syria expert James Denselow. He added that the armed opposition was growing increasingly diverse, and that recent history in Iraq and Lebanon meant there was no shortage of regional knowledge for such attacks.

But according to al-Qa'ida expert Maha Azzam, although yesterday's bombings bore some of the so-called hallmarks of radical Islamist terrorists, the international community should be wary before apportioning blame. "It could just be a group in Syria that's decided to go down that road," she said.

Kofi Annan's peace plan called for President Assad to withdraw his troops from Syria's cities and demanded that opposition fighters halt their attacks.