At least 10 people have been killed in a car bombing in the Syrian capital Damascus, state media report, on the fourth day of a supposed ceasefire.
State TV said women and children were among the victims of the attack in the south-eastern district of Jaramana.
Earlier, activists said government jets had bombed Harasta, in the north-east.
UN envoy Lakhdar Brahimi, who brokered the truce over the Islamic holiday of Eid al-Adha, said he regretted that both sides were not complying with it.
“The situation is bad and getting worse,” he told reporters in Moscow after talks with Russian Foreign Minister Sergei Lavrov.
But Mr Brahimi nevertheless insisted that he would not be discouraged by the apparent failure of his initiative, which he had hoped would allow a political process to develop and lead to a permanent end to hostilities.
“It will not discourage us because Syria is very important and the people of Syria deserve our support and interest,” he added. “We think this civil war must end… and the new Syria has to be built by all its sons.”
At least 110 people – including 39 civilians, 34 rebel fighters and 35 security forces personnel – were killed on Sunday, according to the UK-based activist group the Syrian Observatory for Human Rights (SOHR).
The BBC’s Jim Muir in Beirut says there has been no real pause in hostilities in Syria since the four-day ceasefire supposedly came into force on Friday morning.
On Monday morning, videos were posted online by activists purportedly showing government aircraft bombing Harasta. The footage also showed people being dug out of the rubble and fleeing the area.
Later, state media reported that a “terrorist group” had detonated a car bomb outside a bakery in Jaramana, a predominantly Christian and Druze area of the capital.
A government official told the Associated Press that the explosion had also wounded 41 people and caused heavy damage.
The Local Co-ordination Committees, an opposition activist network, said the car bomb appeared to have targeted a police station.
Overnight, troops attacked rebel positions in the southern suburb of al-Hajar al-Aswad and explosions were heard in nearby Qadam, according to the Syrian Revolution General Council, an opposition activist group.
There were also clashes in the northern city of Aleppo, and the nearby towns of Hayan, Kfar Hamra and Anadan, the Syrian Observatory said.
The SOHR is one of the most prominent organisations documenting and reporting incidents and casualties in the Syrian conflict. The group says its reports are impartial, though its information cannot be verified.
In a separate development on Monday, the Turkish military fired back after a shell fired from Syria landed near the village of Besaslan in the southern province of Hatay, state media said, amid clashes between Syrian soldiers and rebels in the nearby border town of Harim.
Turkish forces have responded to every cross-border shelling since five Turks were killed on 3 October. No injuries were reported on Monday.
According to opposition and human rights activists, more than 35,000 people have been killed since protests against President Bashar al-Assad erupted in March 2011, while the UN estimates at least 20,000 have died.