Syrian jets have fired on Lebanese territory in one of the most serious cross-border violations since the country was plunged into turmoil 18 months ago.
Security officials said four missiles fired hit a remote area on the edge of the Lebanese border town of Arsal. There were no reports of casualties.
The Syrian forces were believed to be chasing rebels in the area, which has been the site of clashes in the past between opposition fighters battling Syrian troops just on the other side of the frontier. Lebanese armed forces have previously detained people in the region caught trying to smuggle weapons into Syria from Lebanon.
Syrian shells have hit Lebanese territory in the past but the air raid appears to be the most serious violation. Several Lebanese, including a journalist, have been killed and dozens wounded by fire coming from the Syrian side.
Meanwhile inside Syria, troops shelled rebel-held areas around the country including the northern city of Aleppo, Syria's largest, and the Damascus neighbourhood of Hajar Aswad, activists said. The British-based Syrian Observatory for Human Rights and the Local Co-ordination Committees also reported clashes between troops and rebels.
And in Geneva, an independent UN panel confirmed that an increasing number of "foreign elements," including jihadis, are now operating in Syria, in its first report to say that outsiders have joined a war spiralling out of control. The investigative panel appointed by the Human Rights Council says some of these forces are joining armed anti-government groups while others are operating on their own.
The Syrian uprising, which began with largely peaceful protests, has since morphed into a deadly armed insurgency. Hundreds of people are killed every week as the government increasingly relies on air power to try and crush the rebels. Activists say more than 23,000 have been killed in the conflict.
Rebels deny that foreigners had any role starting the revolt, saying Syrians were seeking increased freedom from the regime. But as the conflict drags on, some rebels have acknowledged the presence of small numbers of foreigners among their ranks.
The UN panel also accused government forces and pro-regime militiamen known as "shabiha" of war crimes and crimes against humanity including murder, summary executions, torture, arbitrary arrests, sexual violence and abuse of children. It also accused anti-government armed groups of war crimes including murder, extrajudicial execution and torture.
Human Rights Watch said it documented more than a dozen extrajudicial and summary executions by opposition forces. It said three opposition leaders who were confronted with evidence of extrajudicial executions said those who killed deserved to be killed, and that only the "worst criminals were being executed."