Thousands of people took to the streets of Sri Lanka's capital Monday to protest U.S. support of a proposed United Nations resolution condemning alleged human rights violations during the country's civil war.

The U.N. Human Rights Council is taking up the measure during a month-long session, which opened Monday in Geneva, Switzerland.

Sri Lankan Cabinet ministers joined pro-government demonstrators in Colombo to denounce the measure. Protesters marched toward the U.S. embassy in the capital, chanting anti-American slogans. The United States supports the resolution demanding accountability from Sri Lanka and reforms leading toward national reconciliation.

A U.N. report issued last year said tens of thousands of civilians were killed during the final phase of the military's war with the Tamil Tiger rebels. The nearly three-decade conflict ended in May of 2009 with the defeat of the rebels.

The proposed U.N. resolution urges Sri Lanka to investigate alleged war crimes committed by the military during the last months of the war, including the shelling of hospitals. Sri Lanka denies the allegations.

The government appointed its own commission to probe the conflict, which cleared security forces of targeting civilians during the final stages of the conflict.