The United Nations is blaming the Syrian government for an attack on a village Thursday that killed more than 150 people.

U.N. Secretary General Ban Ki-moon said the massacre casts “serious doubts” on Syrian President Bashar al-Assad's commitment to a U.N.-backed peace plan.

U.S. Secretary of State Hillary Clinton said Friday that credible reports provided indisputable evidence government forces deliberately murdered innocent civilians.

The U.N. Security Council is currently debating tough new sanctions on Syria, but Russia has once again threatened to veto any sanctions.

Syrian opposition activists say up to 220 people died when government forces backed by tanks and helicopters shelled the village of Tremseh.