Syria in full-scale civil war - UN

Syria is now in a full-scale civil war, UN peacekeeping chief Herve Ladsous says, as UN observers report being fired on as they tried to enter a town feared to be the focus of a new massacre.

US Secretary of State Hillary Clinton has warned Washington will find it hard to support the extension of the observer mission beyond next month if the government of President Bahar al-Assad's regime continues to show "contempt" for a UN-backed ceasefire that was supposed to go into effect from April 12.

Asked whether he believed Syria is in a civil war, Ladsous told reporters: "Yes I think we can say that. 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.

"I think there is a massive increase in the level of violence, so massive indeed that in a way it indicates some change of nature," Ladsous added.

"Now we have confirmed reports of not only of the use of tanks and artillery but also attack helicopters."

The under-secretary-general for peacekeeping operations is the most senior UN official to indicate he believes there is a civil war. UN leader Ban Ki-moon said last week that he believed it was "imminent".

The UN Supervision Mission in Syria had been trying to reach the northwestern town of Al-Haffe, a Sunni Muslim enclave in a region mainly populated by members of Assad's Alawite minority, where hundreds of civilians are reported trapped by an army siege of holed up rebel fighters.

The mission said it had received reports of "a large number of civilians, including women and children trapped inside the town and are trying to mediate their evacuation".

At least 120 people have been killed in the fighting in and around Al-Haffe over the past week, including 68 troops, 29 civilians and 23 rebel fighters, with hundreds wounded, according to the Britain-based Syrian Observatory for Human Rights.

The UN observers were forced to abandon their attempt to reach the town on Tuesday when an angry crowd in a nearby pro-government village threw rocks and metal bars at them, and unknown assailants then fired on them.

Ladsous said one military observer came close to being hit by a bullet. "We thought he was injured but in fact the bullet did not enter him but hit his boot.

"There were many impacts that hit the car, so it was deliberate," he added.

Another UN official said the crowd that surrounded the UN convoy was carrying government flags and at least 20 bullets hit the car carrying the observers.

Clinton said renewing the mission would be difficult without progress in implementing the six-point peace plan brokered by UN-Arab League envoy Annan, and also hit out at Moscow for sending attack helicopters to its Damascus ally.

"We are concerned about the latest information we have that there are attack helicopters on the way from Russia to Syria, which will escalate the conflict quite dramatically," Clinton said.

"We have confronted the Russians about stopping their continued arms shipments to Syria. They have from time to time said we shouldn't worry, that everything they're shipping is unrelated to their actions internally. That's patently untrue."

Photo: AAP