Imad Mughnieh's body may be back in Beirut and the tangled wreckage of his bombed car towed away by the police but the shattering fallout of the Hezbollah commander's assassination in Syria was still reverberating through the increasingly isolated regime in Damascus yesterday.

The administration, already under pressure from an international investigation into a truck bomb that killed Rafiq Haririexactly three years ago, faced fresh calls from President Bush for tighter sanctions for hosting one of the world's most wanted terrorists.

Analysts said that President Assad of Syria will be under even more pressure to explain to Iran how he let one of its key assets be murdered yards from a base of the Iranian Mukhabarat [intelligence service].

Mughnieh's killing was another blow for Mr al-Assad. Mr Hariri's murder was widely blamed on Damascus and led to protests that forced Syria to withdraw its forces from Lebanon, where they had played a dominant role for three decades.

That blow to Syria's prestige was compounded last summer by an Israeli airstrike which destroyed what some analysts believe may have been a nascent nuclear facility or chemical weapons plants deep inside the country. Then, as now, Syria appeared confused and weak, its stunned silence gradually giving way to contradictory denials from various official sources.

“In terms of military deterrence Syria has taken a huge hit and they have to make it back. In this region you have to look tough,” said Meir Javendafar, an expert on Iran at the Middle East Economic and Political Analysis Company in Tel Aviv.

Sensing that weakness, Washington was quick to pile on the pressure. Mr Bush ordered expanded financial sanctions against senior Syrian officials whom he accused of actions that “undermine efforts to stabilise Iraq”, where Syria is accused of sending Islamist extremists and weapons. He also charged Syria, a major backer of the Shia militia Hezbollah, with meddling in Lebanon and fermenting problems for Beirut's pro-Western Government.

“I wish to emphasise ... my ongoing concern over the destabilising role Syria continues to play in Lebanon, including its efforts to obstruct, through intimidation and violence, Lebanon's democratic processes,” Mr Bush said.

The most intense pressure is likely to come from Iran, which lost, in Mughnieh, a vital asset in its covert, anti-Israeli and anti-American network. The fact that the hit took place in Damascus may raise suspicions that elements of the Syrian security apparatus were infiltrated or even turned.

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