The U.N. human rights chief has called on the Security Council to strengthen the suspended U.N. observer mission in Syria.

U.N. High Commissioner for Human Rights Navi Pillay also called for the Syrian conflict to be referred to the International Criminal Court in the Hague, a move Russia would likely block.

Pillay spoke after briefing the council Monday in New York. She said the flow of arms to both the Syrian government and the opposition risks escalating the conflict, which "must be avoided at all costs."

She said anti-government forces are accused of using children as human shields, and said if the Syrian government grants her staff access, they will investigate the claim.

U.N. forces in Syria repeatedly came under fire before the U.N. suspended the 300-member mission last month.