Security forces in Syria on Sunday hunted those behind a car bomb that killed 17 people as analysts said the attack could have been aimed at splitting Syria's alliance with Iran or deterring it from becoming too friendly with the West.
Saturday's bombing near a Shiite shrine in Damascus, one of the deadliest attacks in the country in more than a decade, drew worldwide condemnation, including from the United States which has repeatedly accused Syria of fuelling unrest in Iraq.
A columnist for Jordan's semi-official daily Al-Dustur blamed Israel's spy agency Mossad.
The car packed with 200 kilos (440 pounds) of explosives blew up near a security checkpoint on a road to Damascus airport in what Interior Minister General Bassam Abdel Majid called as "a terrorist act."
All the casualties were civilians, he told state television, adding: "A counter-terrorist unit is trying to track down the perpetrators."
"No group can be above suspicion because of conflicting regional interests but above all due to Syria's contradictory regional position," Ryad Kahwaji, a Dubai-based analyst, told AFP.
"An ally of Iran, at the same time it is holding indirect peace talks with Israel on condition -- according to Israel -- that it distances itself from Tehran," he said.
"Damascus as a consequence is trying to reassure Tehran that the peace will not be at the expense of their alliance," Kahwaji said, but added: "This could be a message to Syria to abandon its alliance with Iran."
Razzouk Ghawi, a Syrian political analyst, believes the attack was a bid to torpedo improving relations between Damascus and Western capitals.
"The latest positive political developments in Syria's relations, notably with France, strengthen Damascus's international position and this displeases Israel," he said.
Ghawi ruled out any link between the attack and community strife in Syria, saying: "This is a political matter, not a community one."
The rare attack in a country known for its iron-fisted security struck the teeming Shiite neighbourhood of Sayeda Zeinab.
The district draws tens of thousands of Shiite pilgrims from Iran, Iraq and Lebanon each year to pray at the tomb of Zeinab, daughter of Shiite martyr Ali and granddaughter of the Muslim prophet Mohammed.
"It's a US-backed Israeli conspiracy to destabilise the Syrian regime and create enough chaos to produce an opposition that would develop and grow under the sponsorship of Israel and the United States," Hashem al-Khaledi said in an editorial for Al-Dustur newspaper in Amman.
"They seek to topple the regime of President Bashar al-Assad, who is seen by the United States and Israel as an obstacle facing their schemes in the region."
Al-Watan, which is close to the Syrian government, said: "The list is long of those who refuse to let Syria live in security and peace. It begins with Israel, passes via the information services and militias deployed in (neighbouring) countries and ends with Islamist groups which interpret religion badly."
Lebanon's Shiite Hezbollah on Sunday also condemned the "atrocious attack," saying it serves only "the enemy of the 'ummah' (nation) in creating chaos and instability in the region."
The US State Department has closed its consular section in Damascus until October 5 for all but emergency services for American citizens.
Saturday's blast was the deadliest since a spate of attacks in the 1980s blamed on the Muslim Brotherhood left nearly 150 dead.
