Three women were among seven killed in the bombardment of the opposition bastion of Douma, the Britain-based Syrian Observatory for Human Rights said.

The Local Coordination Committees (LCC), a grassroots network of activists, said regime forces have been shelling Douma for three days.

Elsewhere in Damascus province, five civilian men were killed in Saqaba, the Observatory said, adding that some of them had been "slaughtered" with knives.

"This kind of killing has become common in recent weeks," Observatory head Rami Abdel Rahman told AFP, adding that an independent investigation was needed.

In the same region, a man, his wife and their child were killed when their house in the town of Irbin was hit by a shell, the Observatory said.

It also reported that regime forces shot dead a man at a checkpoint in the Damascus province town of Al-Tal, while a student was shot dead on the outskirts of Ashrafiyet Sahnaya.

Two others were killed during the night in Kfar Batna, also in Damascus province, while one woman died in Maadamiyat al-Sham in the same province.

Shelling and shooting by regime forces over various districts of Homs city -- including Khalidiyeh, Bab Tadmur, Jourat al-Shiah and Safsafa -- killed five people, the Observatory said.

It reported the Homs killings after warning that more than 1,000 families were besieged in several districts of the city, which have been pounded intermittently by regime forces for several months.

In the province of Homs, five people were killed in the village of Farhaniyeh when regime forces bombed their area, the watchdog added.

Elsewhere, the Observatory said, four regime troops were killed during the night, one in a blast in Damascus and three in clashes in rebel bastion Rastan in Homs province.

Anti-regime activist Abu Rawan described the shelling of Rastan as "insane."

"In addition, every car that enters or leaves the town gets shot at with heavy machinegun fire," he told AFP via Skype.

In the southern province of Daraa, two rebel leaders were killed in clashes near a regime checkpoint.

The Observatory said at least 100 people were arrested by regime forces in Damascus, while the LCC reported house-to-house raids and mass arrests in the central province of Hama, one of the first to join the anti-regime uprising.

At least 54 people died in violence on Friday -- 43 civilians, eight regime troops and three rebel fighters, the watchdog said.

According to the Observatory, more than 14,400 people have been killed since the uprising against President Bashar al-Assad's regime erupted in mid-March 2011.