The head of the United Nations' peacekeeping operations has said that the situation in Syria now amounts to a full-scale civil war as witnesses on the ground described fresh shelling on Homs and heavy fighting in other cities.
"Yes, I think we can say that," Herve Ladsous, the head of the UN's Department of Peacekeeping Operations, said in New York on Tuesday, when asked whether he believed Syria was now in a state of civil war.
"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."
Kieran Dwyer, a spokesman for the UN peacekeeping department, told Al Jazeera that Landous' description was "related to what is going on in the last five days."
"What we've seen in the last five days is a huge upscaling of the military confrontation," he said. "[It's by] both sides, at a huge cost to the civilian population."
Syria's foreign ministry responded to the remarks on Wednesday, saying that they represented an unrealistic description of the conflict.
"Talk of civil war in Syria is not consistent with reality... What is happening in Syria is a war against armed groups that choose terrorism," state news agency SANA quoted a ministry statement as saying.
As violence continued on the ground, activists said government forces continued to shell rebel strongholds in the city of Homs on Wednesday.
Live amateur footage showed appeared to show rocket attacks destroying a number of buildings in the city's al-Khaldiyeh neighbourhood.
The UN mission in Syria posted this video, shot in and around Homs, which shows the aftermath of some shelling [UNSMIS]
A day earlier, UN observers filmed helicopters over the city, saying they saw fire coming from them.
There have been repeated claims in recent weeks that government forces have resorted to aerial attacks in the military crackdown on rebels.
The US expressed worries on Tuesday that Russia may be sending Syria attack helicopters and rejected Russian claims that its arms transfers to Syria were unrelated to the conflict.
Addressing a forum in Washington, Hillary Clinton, the US secretary of state, said: "We have confronted the Russians about stopping their continued arms shipments to Syria. They have, from time to time, said that we shouldn't worry - everything they are shipping is unrelated to their [the Syrian government's] actions internally.
"That's patently untrue."
The UN has about 300 observers on the ground charged with monitoring both sides' compliance with a peace plan mediated by Kofi Annan, the former secretary-general turned UN envoy.
But the observers have been unable to reach certain parts of the country, including al-Haffa, a besieged coastal town where a crackdown has been feared.
The mission said it was barred from entering al-Haffa by "angry crowds" who threw rocks and metal rods at their vehicles.
Meanwhile, the opposition Free Syrian Army (FSA) said it had withdrawn from al-Haffa on Tuesday evening.
"The town and villages of al-Haffa were subjected to aerial, tank and rocket bombardment, as well as a suffocating siege by regime forces and thugs," the FSA said.
State television said government forces had "cleansed terrorist groups" from the area and restored calm.
Clashes started a week ago between rebels and security forces who were setting up checkpoints to tighten their grip on the strategic town, which lies close to the port city of Latakia as well as the Turkish border.
It has allegedly been used by rebels to smuggle people and supplies.
Most accounts of violence cannot be independently verified, as Syria restricts access for journalists.