Rights investigator warns of growing sectarian violence

Mr Pinheiro, who heads an commission investigating abuses, said the conflicting was pitting majority Sunni rebels against government forces supported by the country's religious and ethnic minorities.

He warned the bulk of the victims of the nearly two-year war were civilians. and blamed both sides for abuses including torture and illegal executions.

He found that foreign fighters, many linked to extremist Sunni groups, are infiltrating into Syria. They are operating in independent units that co-ordinate actions with the Free Syrian Army - the Western-backed armed group which is the rebels' main military force.

Mr Pinheiro said in Brussels: "The commission is extremely worried by the presence of foreign fighter who are not fighting for human rights and democracy.

"By their own admission, they are very proud of their breaches of humanitarian law."

Although Mr Pinheiro visited Damascus, the panel was not allowed into Syria and was forced to compile its report from interviews with Syrians who have fled the conflict.

Hundreds of thousands of Syrians have escaped into Turkey, Jordan, Lebanon and Iraq.

The panel noted that anti-government rebels were hiding in Syrian cities where they were "failing to distinguish themselves" from the civilian population, triggering strikes by government artillery and air force.

"As battles between government and anti-government armed groups approach the end of their second year, the conflict has become overtly sectarian in nature," it said.

It added that Christians, Armenians, Druze and others have largely aligned themselves with President Bashar Assad's regime.

"The commission has received credible reports of anti-government groups attacking Alawites and other minority communities."

Almost all of the 80,000 Christians who used to live in the central town of Homs, the scene of intense fighting between the warring sides, have fled to Damascus or Beirut.

"We think this is a war where no military victory is possible," Mr Pinheiro said.

"It is a great illusion that providing arms to one side or the other will help to end it."