Syria's new cabinet has begun work, after Prime Minister Riad Hijab defected and denounced Damascus's "terrorist regime".
Information Minister Omran al-Zoubi said Mr Hijab had not yet
appeared in person and he rejected reports of other ministerial
defections.
Meanwhile, Iran's security chief has made an unexpected visit to Damascus in an apparent step change in diplomacy.
Tehran says it is planning a conference aimed at solving the Syrian crisis.
The staunchest regional ally of Syrian President Bashar
al-Assad, Tehran is also trying to secure the release of a group of
Iranians abducted by rebels from a bus in Damascus on Saturday.
'US held responsible'
An unconfirmed report from the rebels has suggested that three
of the 48 hostages they are holding have been killed by army shelling.
Saeed Jalili, who heads Iran's supreme national security
council and is considered a senior aide to Supreme Leader Ayatollah Ali
Khamenei, was due to meet Bashar al-Assad and several other top
officials.
It also emerged that Foreign Minister Ali Akbar Salehi was travelling to Turkey for talks in Ankara.
Iran's Deputy Foreign Minister Hossein Amir Abdollahian has said it holds the US responsible for the hostages' safety.
He said the US was supporting "terrorist groups" and despatching
weapons to Syria, and was therefore responsible for the lives of those
abducted.
The rebels have claimed that the group are members of the
Revolutionary Guard. Tehran says they are pilgrims who had been heading
for a Shia religious site.
'Business as usual'
Caretaker Prime Minister Omar Ghalawanji headed an emergency
cabinet meeting on Monday, stressing that all the ministers were there.
He was due to chair a further session on Tuesday.
The BBC's Jim Muir, in neighbouring Lebanon,
said state media were giving the impression of it being business as
usual in Damascus.
Opposition activists said that apart from the prime minister,
two other ministers had also defected and a third - Finance Minister
Mohammad Jalilati - was arrested as he tried to escape.
But footage of the cabinet on state TV showed two of the
ministers who had supposedly defected and Syria's information minister
played down the significance of Mr Hijab's departure.
"We haven't heard anything from the former prime minister and
he didn't appear on TV," Omran al-Zoubi was quoted as saying by Syrian
state news agency Sana.
Syria was a state of institutions, the information minister
said, and the flight of some of its individuals would not affect the
state, however prominent they were.
'Safe location'
Riad Hijab, appointed as prime minister less than two months ago, is the most prominent Syrian figure to defect so far.
Although his whereabouts are unclear, his spokesman appeared
on al-Jazeera TV in neighbouring Jordan saying that the prime minister
had fled Syria with his family and was in "a safe location".
"I have defected from the terrorist, murderous regime and
[am] joining the holy revolution," ran Mr Hijab's statement read by his
spokesman Mohammed el-Etri.
France said the Assad government was "doomed" and White House
spokesman Jay Carney said such high-level defections signalled that
President Assad's grip on power was "loosening".
"If he cannot maintain cohesion within his own inner circle,
it reflects on his inability to maintain any following among the Syrian
people that isn't brought about at the point of a gun," he said.
On the ground in Syria, the army is reported to have stepped up its bombardment of Aleppo.
Government forces are trying to dislodge rebel fighters who have taken control of some areas of Syria's second city.
Opposition activists report intense attacks on rebel-held areas on the north-east and south-west sides of the city.
State TV said troops had clashed with "terrorist groups" in
several places, inflicting heavy losses and recapturing two police
stations.