GENEVA (REUTERS) - Syrians in "leadership positions" who may be responsible for war crimes have been identified, along with units accused of perpetrating them, United Nations investigators said on Monday.

Both government forces and armed rebels are committing war crimes, including killings and torture, spreading terror among civilians in a nearly two-year-old conflict, they said.

The investigators' latest report, covering the six months to mid-January, was based on 445 interviews conducted abroad with victims and witnesses, as they have not been allowed into Syria.

Ms Karen Konig AbuZayd, one of four UN commissioners on the team of some two dozen experts, told Reuters: "We have information suggesting people who have given instructions and are responsible for government policy. People who are in the leadership of the military, for example."

The latest list of suspects, building on lists drawn up in the past year, remains secret. It will be entrusted to UN High Commissioner for Human Rights, Ms Navi Pillay, upon expiry of its current mandate at the end of March, the report said.

Ms Pillay, a former judge at the International Criminal Court (ICC), said on Saturday Syrian President Bashar al-Assad should be probed for war crimes and called for immediate action by the international community, including possible military intervention.

The death toll in Syria is likely approaching 70,000 people, Ms Pillay told the Security Council last week in a fresh appeal for it to refer Syria to the ICC, the Hague-based war crimes court.

Government forces have carried out shelling and aerial bombardment across Syria, including Aleppo, Damascus, Deraa, Homs and Idlib, the independent UN investigators said, citing corroborating evidence gathered from satellite images.

"In some incidents, such as in the assault on Harak, indiscriminate shelling was followed by ground operations during which government forces perpetrated mass killing," it said, referring to a town in the southern province of Deraa where residents told them that 500 civilians were killed in August.