Violence erupted in two Syrian provinces yesterday, with a rights group reporting 10 civilians dead in an army mortar attack and 12 soldiers killed in a fire-fight with rebel gunmen as UN monitors sought to shore up a shaky ceasefire.

The British-based Syrian Observatory for Human Rights, which tracks the 13-month-old uprising against President Bashar al Assad, said nine members of one family died in mortar bomb blasts in a village in the northern province of Idlib.

In the eastern Deir al-Zor province, troops hit back with mortar and heavy gunfire after losing a dozen of their own to insurgents, killing at least one villager and destroying a school building, the anti-Assad Observatory added.

The United Nations says Syrian forces have killed more than 9000 people since the uprising began in March 2011. A UN ceasefire brokered in mid-April led to a brief lull but failed to halt the conflict. Rebels starved of funding and ammunition appear to be stepping up a bombing campaign.

Explosions blew the fronts off buildings in the northwestern city of Idlib on Monday, killing nine people and wounding 100, including security personnel, according to state television, which blamed the blasts on "terrorist" suicide bombers. Damascus has accused the United Nations of turning a blind eye to rebel ceasefire violations, although Secretary-General Ban Ki-moon condemned the Idlib blasts and a rocket attack on the central bank in the capital as "terrorist bomb attacks".

The UN now has 30 truce monitors in Syria, a nation of 23 million people, and expects to have 20 more of the planned 300-strong mission on the ground by the end of the week.

Their commander, Norway's Major General Robert Mood, has said progress is possible despite the enormity of their task.

"We will be only 300 but we can make a difference," he said on arrival in Damascus this week.

Western governments have lost patience with Mr Assad, accusing him of breaking promises made to UN-Arab League envoy Kofi Annan that he would order troops and tanks back to barracks.