Syrian warplanes bombarded a besieged rebel-held district of Homs, southern Deraa and insurgent areas in Damascus's outskirts on Saturday in what appeared to be intensifying assaults in the west of the country, monitors said.

Much of western Syria is covered by an ongoing but shaky ceasefire between the government and rebels that took effect on Dec. 30, but fighting has rumbled on, with warring sides accusing each other of truce violations as peace talks loom in Geneva next week.

On Damascus's northeastern outskirts, Syrian government forces attacked the rebel-held Qaboun and Barzeh districts with rockets and shells and killed at least nine people, the British-based Syrian Observatory for Human Rights monitoring group said.

A Reuters witness heard the sounds of heavy bombardment coming from the area. There was no immediate comment from the government side.

To the north, Syrian jets bombarded the last rebel-held district of Homs, al-Waer, killing at least two people and raising the death toll from nearly two weeks of air strikes there to more than 20, an activist and the Observatory said.

A military media unit run by Damascus's ally Hezbollah said insurgents in al-Waer had been attacked by warplanes and artillery after rebel sniper fire hit neighbouring areas.

For months, al-Waer had been spared much of the intense violence raging elsewhere, as the government tried to do a deal with rebels to let them leave with their families. Similar agreements elsewhere in the west have resulted in rebels leaving with light weapons and heading mostly for Idlib province.

The opposition says such accords are part of a government strategy to forcibly displace populations from opposition-held areas after years of siege and bombardment.

In September, some 120 rebel fighters and their families left al-Waer in agreement with the government, but there have been no further reports of insurgents leaving. The Observatory estimates several thousand rebels remain there.

In the southern province of Deraa, government and Russian warplanes stepped up their bombardment of rebel-held areas, carrying out at least 70 air strikes on Friday and Saturday, on Deraa city and towns to the east, the Observatory reported.

At least four people were killed in the town of Umm al-Mayadhin, and one person in Busra al-Sham, it said.

The ceasefire deal is backed by Russia, which is supporting Syrian President Bashar al-Assad, and by Turkey, which backs some rebel groups, but fighting has continued almost since it took effect.

The radical Islamist group Islamic State and Jabhat Fateh al-Sham, the former Syrian branch of al Qaeda, are not included in the ceasefire.