-Syria's state news agency (SANA) on Sunday says a car bomb near a Palestinian refugee camp in a suburb of the nation's capital has killed at least 15 people.

SANA says the explosion in the Damascus suburb of al-Sbeineh late Saturday also wounded several people and caused heavy damage to buildings in the area.

Another explosion was reported Saturday at Rukn Eddin inside capital Damascus, and which targeted a military doctor in front of a hospital.

Press reports added Saturday that Syrian rebels launched attacks on the military, in a campaign increasingly targeting its air power.

Press reported Saturday that at least 111 people were killed, including 35 in Damascus, according to the opposition Local Coordination Committees (LCC) statement.

Government forces also shelled areas of Homs and Aleppo and used tank fire in the Damascus neighbourhoods of Tadamon and Hajar Aswad, press reports added.

Press quoted activists saying this is the second day of a rebel push in Aleppo dubbed "Northern Volcano" targeting security facilities in the city and the surrounding province, including an artillery training school, a compound of the feared air force intelligence and a large army checkpoint.

The clashes in Aleppo were concentrated in the neighborhoods of Hanano, Bustan Al Qasr, Sukkari and Maysar. Activists also reported injuries and damage to buildings.

Press reports indicated that the latest violence shows that government troops are still struggling to regain full control of the city from the lightly-armed rebels nearly five weeks after they stormed their way into it in a surprise offensive.

Activists also reported that rebels also captured an air defense facility in the east of the country near the border with Iraq. Rebels captured the main air defence building in Albu Kamal on the Iraqi border, the Syrian Observatory for Human Rights said. "Preliminary reports" suggested they had seized ground-to-air missiles.

The opposition has claimed advances in the area in recent days. A video released by activists showed soldiers purportedly captured by rebels at the post. The authenticity of the video could not be independently confirmed.

Also on Saturday, Syrian Arab News Agency SANA reported that 225 detainees who had taken part in anti-government protests had been released Saturday.

The amnesty by authorities is the second in a week, after 378 prisoners from Damascus and Homs were freed on Monday, According to SANA.

More clashes were reported on Saturday in Damascus & its countryside, near Aleppo, Hama, Idleb, Homs, Daraa & Deir Ezzour along with their suburbs.

Syrian regime used to blame the blasts and crisis on an "armed terrorist group," the term it uses to describe the rebel Free Syrian Army seeking to topple Syrian President Bashar al-Assad.

The Syrian conflict has its roots in mostly peaceful street protests that started in March 2011. It has since morphed into a civil war, with at least 20,000 people killed so far, rights activists say.