Two car bombs rocked the Syrian capital, Damascus, on Monday, killing at least 10 and wounding scores of others, among them women and children, DPA reported.
A car bomb exploded in an area of Hajar al-Aswad, south of Damascus, inflicting an unspecified number of casualties, Syrian television reported Monday.
The blast came just hours after at least 10 people were killed in a different car bomb explosion in a predominantly pro-regime neighbourhood of the capital.
The two blasts came as the Syrian military launched heavy airstrikes across the country, leaving at least 80 people dead, the Britain-based Syrian Observatory for Human Rights reported.
"We registered more than 60 air raids across the country," the watchdog's director, Rami Abdel Rahman, told dpa.
The Observatory said the raids focused on areas at the outskirts of Damascus and towns across the north-western province of Idlib, where regime forces and rebels have been fighting fierce battles.
Rebels claimed they have taken over three villages near the border with Turkey, which, on Monday, fired back after a Syrian shell landed in the southern Hatay province. No casualties were reported.
"The disruption by the US and some European and Western countries of issuing Security Council statements that condemn the bloody terrorism claiming dozens of lives of women, children and the elderly in Syria can only be interpreted as practical support for terrorism and terrorists," the Syrian Foreign Ministry said in two identical letters addressed to the chairman of the UN Security Council and the UN secretary general.
The blasts and the bombardments came on the final day of the four-day ceasefire marking the Muslim feast of Eid al-Adha, and while UN-Arab League envoy Lakhdar Brahimi was engaged in talks with Russian officials.
"The Syrian crisis is very, very dangerous, the situation is bad and getting worse," Brahimi told reporters in Moscow, where he met Foreign Minister Sergei Lavrov.
"I am terribly sorry ... that this appeal (for a truce) has not been heard, but that will not discourage us. It will not discourage us, because Syria is very important and the people of Syria deserve our support," Brahimi said.
Brahimi, who will also visit China, is rallying support from allies of President Bashar al-Assad to end the 20-month conflict, which has claimed the lives of more than 34,000 people.
Both Russia and China have vetoed three Western- and Arab-backed resolutions at the UN Security Council condemning the Syrian regime for the violence.
The UN envoy is scheduled to brief the UN Security Council later this week, Arab media reported.
Activists said some 500 people have been killed since Friday, when the ceasefire was supposed to start.