The Palestinians' ruling Hamas Party denounced the U.S. on Sunday for vetoing a U.N. Security Council draft resolution condemning an Israeli military offensive in the Gaza Strip and demanding an Israeli troop withdrawal from the territory.

"The American veto represents a political and moral aggression against our people and national cause, an ugly act of racism, and a direct encouragement of the Zionist enemy to commit more crimes and massacres," the militant Islamic group said in a statement.

The draft resolution was brought before the Security Council after errant Israeli shells slammed into an apartment compound in Gaza, killing 18 civilians.

U.S. Ambassador John Bolton said the Arab-backed proposal was "biased against Israel and politically motivated."

At a meeting of the Security Council on Saturday, the draft received 10 votes in favor and four abstentions, and one vote against, from the United States. The U.S. is one of five permanent members of the council with veto power.