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.
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.
- Salva Kiir sacks top South Sudan officials
- Lawyer wants Chinedu to appear in court
- Maji marefu’s futile effort to find stolen property
- Diplomatic passports, special number plates for governors
- Can chickens really be cleverer than a toddler? Studies suggest animals can master numeracy and basic engineering
- Freedom of media under threat in Eastern Africa