The UN human rights commissioner has said that weapons supplied to the Syrian government and opposition are escalating the conflict, and made an appeal for Syria conflict to be referred to the International Criminal Court.
"The provision of arms to the Syrian government and to its opponents is fueling the violence," Navi Pillay told reporters after briefing the UN Security Council on Monday.
"Any further militarisation of the conflict must be avoided at all costs."
Pillay said the government and opposition are carrying out "serious" new rights violations including attacks on hospitals.
She renewed an appeal for the 15-nation council to refer the Syria conflict to the International Criminal Court.
The UN high commissioner said she was now calling the situation in Syria "a non-international internal armed conflict," the legal term for a civil war.
Once that term is used, diplomats say, it means the Geneva Conventions on armed conflict apply.
Saying that both the Syrian government and the opposition groups appear to have committed war crimes, Pillay added that her office "cannot exclude the possibility that some of the killings were perpetrated by armed opponents (of the government)".
But she noted that the "the bulk of the information gathered to date points to the involvement of government-supported
Shabbiha militia responsible for many of the killings, and the use of indiscriminate fire of heavy weapons by the government".
Pillay also called on the Security Council to strengthen the suspended UN observer mission in Syria. She said the mission's presence in Syria remains vital.
The conflict has killed more than 10,000 people since the revolt began in March 2011, according to opposition estimates.
Source of weapons
She did not say where the weapons were coming from, though Russia and Iran are among the Syrian government's key suppliers.
A confidential report submitted by a panel of sanctions-monitoring experts to the Security Council's Iran sanctions committee in May indicated that Syria remains the top destination for Iranian arms shipments, in violation of a UN Security Council ban on weapons exports by the Islamic Republic.
The panel investigated three large illegal shipments of Iranian weapons over the past year.
A US newspaper reported in June that CIA operatives on the ground in southern Turkey were trying to determine which Syrian opposition groups should be armed, even though the Obama administration has said that it has not provided weapons to any anti-government groups.
UN diplomats say Qatar and Saudi Arabia have been transferring arms to Syria's increasingly militarised opposition.
Syrian soldiers defect
On Monday, the army kept up its bombardment of rebel neighbourhoods of the central city of Homs as violence killed at least 30 people across the country, London-based the Syrian Observatory for Human Rights said.
An activist in Homs told AFP news agency via Skype that many civilians remained trapped in the shelling of the Jurat al-Shiah, Khaldiyeh and Old City neighbourhoods of Syria's third-largest city.
"Many neighbourhoods of Homs are still under siege, and it is really hard for us to get food or medicines in," said Khaled al-Tellawy.
In the north, Turkey said that 85 Syrian soldiers defected after fleeing across its border. Among them were a general and other ranking officials, Anatolia news agency cited officials as saying.
Smoke rising above the hills was seen from southern town of Kilis in Turkey where 10,000 Syrian refugees are lodged in containers.
Meanwhile, opposition figures met behind closed doors in Cairo to chart a common vision after criticising a transition blueprint agreed by the major powers at the weekend.
Arab League chief Nabil al-Arabi, who chaired the two-day meeting attended by around 250 opposition figures, urged the factions "not to waste this opportunity" and to "unite".