TRIPOLI, June 8 (Xinhua) -- A U.S. airstrike targeting Islamic State (IS) terrorists in Libya killed three civilians, the Libyan Foundation for Human Rights said on Thursday.

"The U.S. raid on a valley in Bani Walid (city) killed three civilians, who have no links with extremist groups. The victims were traveling in a car unarmed and unwarned," the Libyan human rights organization said in a statement.

"The civilian victims were present with the target Abdal'ati Eshtewi Abu-Setta for social purposes, after their relatives confirmed that they did not take part in any terrorist acts, and were not issued arrest warrants by the security authorities," the statement said.

Abu-Setta was reportedly one of the most prominent IS leaders in Libya wanted by local and U.S. authorities.

The Libyan Foundation for Human Rights also said that, in coordination with the families of the victims, a request for investigation will be presented, holding the UN-backed government and the U.S. administration responsible for their deaths.

The U.S. Africa Command (AFRICOM) on Wednesday said that a U.S. airstrike targeted and killed four IS terrorists, including a senior leader, on the outskirts of Bani Walid, some 180 km southeast of the capital Tripoli.

"In coordination with the Libyan Government of National Accord, U.S. forces conducted a precision airstrike near Bani Walid, Libya, on June 6, killing four ISIS (IS)-Libya militants," AFRICOM said in a statement on Wednesday.

"At this time, we assess no civilians were killed in this strike," the statement said.