By Timour Azhari
Dec 4 (Reuters) - A U.S. air strike killed five Iraqi militants near the northern city of Kirkuk as they prepared to launch explosive projectiles at U.S. forces in the country, three Iraqi security sources said, identifying them as members of an Iran-backed militia.
A U.S. military official confirmed a "self-defense strike on an imminent threat" that targeted a drone staging site near Kirkuk on Sunday afternoon.
A statement by the Islamic Resistance in Iraq, an umbrella group representing several Iraqi armed factions with close ties to Tehran, said five of its members had been killed, and vowed retaliation against U.S. forces.
The group had claimed several attacks against U.S. forces throughout Sunday.
Earlier Sunday, the U.S. military official said U.S. and international forces were attacked with multiple rockets at the Rumalyn Landing Zone in northeastern Syria, but there were no casualties or damage to infrastructure.
Iraqi armed groups have claimed more than 70 such attacks against U.S. forces since Oct. 17 over Washington's backing of Israel in its bombardment of Gaza.
The attacks paused during the recent Israel-Hamas ceasefire but have since resumed.
The U.S. in November launched two series of strikes in Iraq against what it said were Iran-aligned armed groups who had engaged in attacks against their forces.
Those strikes killed at least 10 militants who were identified both as members of shadowy militia Kataeb Hezbollah and of Iraq's Popular Mobilisation Forces, an official security institution composed mainly of Shi'ite Muslim armed groups.
Iraq's government condemned those strikes as escalatory and a violation of Iraqi sovereignty.
The United States has 900 troops in Syria and 2,500 in Iraq on a mission it says aims to advise and assist local forces trying to prevent a resurgence of Islamic State, which in 2014 seized large swaths of both countries before being defeated.
(Reporting By Timour Azhari; Editing by Sharon Singleton and Diane Craft)