Fresh fighting has erupted in various parts of Syria, activists say, with at least five people reported killed by government shelling in the south.
The violence comes despite both sides rejecting the characterisation of the conflict as civil war by a UN official.
The Syrian government insists it is fighting terror groups and rebels say they are defending a peaceful uprising.
Both sides have predicted a massacre at the western mountain town of Haffa, where rebel fighters are besieged.
Early on Wednesday the Local Co-ordination Committees, a network of Syrian activists, said the latest violence included shelling in the town of Bosra el-sham near Deraa in the south.
They said at least five people had been killed. On Tuesday, activists said at least 60 people had died across the country.
Such claims cannot be verified independently as Syria severely restricts journalists' freedom of movement.
On Tuesday the head UN peacekeeping operations, Herve Ladsous, characterised the conflict as "a civil war" during an interview in New York.
He Ladsous told a small group of reporters: "Clearly what is happening is that the government of Syria lost some large chunks of territory, several cities to the opposition, and wants to retake control."
However there were angry reactions by both sides. The government restated its position that it is combating foreign-backed terrorist groups.
Opposition groups say this was not a civil war, but a peaceful uprising.
The UN and the US have warned of an alarming escalation in violence in Haffa, amid reports of a build-up of government forces around the town.
UN monitors say they were shot at and prevented from reaching the town on Tuesday. Monitors judged the situation to be "unsafe" and turned back, a UN spokeswoman said.
As they were leaving, an angry crowd threw stones and metal bars at the UN team before unknown assailants opened fire, she added.
The UN monitors are in Syria to observe the implementation of a peace plan brokered by UN-Arab League envoy Kofi Annan. However, a ceasefire which was supposed to come into effect on 12 April never took hold.
Also on Tuesday, the US expressed renewed concern about Russian arms supplies to Syria. Secretary of State Hillary Clinton said the latest information indicated that attack helicopters were on their way from Russia to Syria - a move she said would escalate the conflict dramatically.
Earlier this month, activists said Syrian government forces killed 108 people in the region of Houla, in Homs province, and 78 people in the village of Qubair, in Hama province.