The International Committee of the Red Cross has said it now considers the Syrian conflict a civil war, as activists reported intense battles between rebels and government forces in the capital, Damascus.
The Geneva-based group's assessment could have implications for prosecutions for war crimes and means that international humanitarian law applies throughout the country. Also known as the rules of war, humanitarian law grants all parties in a conflict the right to use appropriate force to achieve their aims.
"We are now talking about a non-international armed conflict in the country," ICRC spokesman Hicham Hassan said on Sunday.
Previously, the Red Cross committee had restricted its assessment of the scope of the conflict to the hotspots of Idlib, Homs and Hama. But Hassan said the organisation concluded that the violence was widening.
"Hostilities have spread to other areas of the country," Hassan said. "International humanitarian law applies to all areas where hostilities are taking place."
The qualification means that people who order or commit attacks on civilians including murder, torture and rape, or use disproportionate force against civilian areas, can be charged with war crimes in violation of international humanitarian law.
War crimes prosecutions would have been possible even without the Red Cross statement. But Sunday's pronouncement adds weight to any prosecution argument that Syria is in a state of war - a prerequisite for a war crimes case.
Josh Lockman, an international law professor at the University of Southern California, said the assessment does not make any significant difference on the ground, but is "of tremendous significance for the long term".
"With this application of international humanitarian law to the conflict, key regime officials could be held responsible for both massacres against civilians and also for the treatment of captured combatants, in this case rebel fighters, to the degree they're abused, harmed or killed," he told Al Jazeera.
Protection of civilians
Although the armed uprising in Syria began more than a year ago, the committee had hesitated to call it a civil war - though others, including United Nations officials, have done so.
That is because the rules of war override and to some extent suspend the laws that apply in peacetime, including the universal right to life, right to free speech and right to peaceful assembly.
The rules impose limits on how fighting may be conducted, so as to protect civilians and ex-combatants not taking part in the hostilities.
They require the humane treatment of all people in enemy hands and the duty to care for the wounded and sick. It also
means parties to the internal conflict are entitled to attack military targets, but not civilians or civilian property.
As violence continued on the ground, a monitoring group said clashes in Damascus marked the "most intense" fighting in the capital since the start of the revolt 16 months ago.
"The regular army fired mortar rounds into several suburbs" where fighters of the Free Syrian Army are entrenched, said Rami Abdel Rahman, head of the Syrian Observatory for Human Rights.
He said the fighting was heaviest in the Tadamon, Kfar Souseh, Nahr Aisha and Sidi Qadad neighbourhoods.
"The security forces are attempting to take control of these neighbourhoods, but so far they have not succeeded," he added.
The Local Co-ordination Committees activist network said plumes of black smoke were billowing out of Tadamon and that loud explosions were heard in Nahr Aisha.
The Observatory and the LCC both said more than 50 people were killed across the country on Sunday.
Syria denial over Tremseh
Meanwhile, Syria has denied accusations by special envoy Kofi Annan that state forces used heavy weapons or helicopters in clashes in the village of Tremseh last week, where activists said there was a massacre of more than 100 people.
Jihad Makdissi, spokesman for the foreign ministry, said on Sunday that security forces killed 37 fighters and two civilians in a campaign against the village, from which the government said rebels were launching attacks on other areas.
"Government forces did not use planes, or helicopters, or tanks or artillery. The heaviest weapon used was an RPG [rocket-propelled grenade]," Makdissi told reporters in Damascus.
But a freelance photojournalist who visited Tremseh after Thursday's assault told Al Jazeera that he "found obvious proof of heavy weapons".
"Everyone was very nervous trying to show us what happened in the town. There were marks of shelling [by] mortars," said Daniel Leal Olivas.
A UN Supervision Mission in Syria (UNSMIS) entered Tremseh on Sunday for a second day to assess the casualties and damage in the village.
The group released a statement on its inspections, saying that the village had come under attack by "direct and indirect weapons, including artillery, mortars and small arms".
"The integrated patrol, comprised of specialised civilian and military experts, observed over 50 houses that were burned and/or destroyed. Pools of blood and brain matter were observed in a number of homes," said the statement, which did not identify the perpetrators of Thursday's attack or estimate the number of dead.