Syrian regime warplanes have carried out several air raids on opposition-held areas in and around Damascus, while fresh clashes between troops and opposition forces have erupted in the eastern and southern suburbs of the capital, according to an activist group.

The regime also used fighter jets to bombard the opposition-held towns of Yabroud, Douma and Harasta, east of Damascus, as well as Sbeineh, southwest of the capital, the Syrian Observatory for Human Rights (SOHR) said on Monday.

"At least one civilian was killed in an air strike on Qaboon" in northeast Damascus, SOHR said, "while regime troops pounded the district of Jobar" in the east.

Meanwhile, "fierce clashes raged on the edges of Jobar [in eastern Damascus], near Abbasiyeen Square", according to SOHR, which relies on a broad network of activists, doctors and lawyers for its reports.

The opposition forces view the square as a strategic target because it lies well within the confines of Damascus, President Bashar al-Assad government's main bastion of power.

SOHR also reported the regime army's use of heavy artillery fire on Yarmuk in southern Damascus, with tanks also striking other opposition enclaves nearby.

Elsewhere in Syria, regime jet fighters hit targets in the northeastern city of Raqqa as well as an area near the regime-held Base 17 in the eponymous province.

Raqqa's provincial capital fell into opposition hands in early March, and revolution fighters have since been fighting to gain control of Base 17, one of the regime army's few remaining bastions in the province.

In coastal Syria, "the regime army launched a massive operation ... in the north of Latakia province", near the Turkish border, attacking opposition-held villages, the pro-regime Al-Watan newspaper said.

According to a preliminary toll for Monday, at least 22 people were killed in violence across Syria, SOHR said.

Secret prisons

In yet another development on Monday, a Syria-based human rights group said in a report that Assad's military unit in charge of “protecting” Damascus was running secret prisons holding hundreds of suspected regime opponents.

The Violations Documentation Centre said the regime army's Fourth Division was running detention centers in its bases in and around Damascus.

The division is commanded by Maher Assad, the president's younger brother. It is considered a pillar of military forces and is charged with defending the capital, the seat of Assad's power.

The center, which has tracked the dead, wounded and missing since the start of the uprising in March 2011, said it interviewed former detainees, who had been held in small crowded cells and beaten by guards.

Bashar El-Ahmed, a 31-year-old schoolteacher, said he was taken blindfolded to the detention center and realized after arrival that he was underground.

He said guards beat him with batons, electric prods and cables. The report said El Ahmed was accused of human right activism.

The claims could not be independently verified, but other rights groups, including the US-based Human Rights Watch, have said thousands of opposition members, protesters and their families have been detained since the revolt against Assad's rule started in March 2011.

PHOTO CAPTION

This citizen journalism image shows buildings damaged …more in a government airstrike and shelling at Bostan Pasha district in Aleppo, northern Syria, Friday, April 12, 2013.

Al-Jazeera