TRIPOLI, Feb 19 (Reuters) - U.S. warplanes carried out air strikes early on Friday morning in the western Libyan city of Sabratha, where Islamic State militants operate, killing as many as 40 people.
A U.S. military spokesman said the attacks targeted a senior Tunisian militant linked to attacks in Tunisia last year.
Sabratha's mayor, Hussein al-Thwadi, told Reuters the planes struck at 3.30 a.m. (0130 GMT), hitting a building in the Qasr Talil district in which foreign workers were living. He said 41 people had been killed and six wounded. The death toll could not immediately be confirmed with other officials.
Tunisian security sources have said they believe Tunisian Islamic State fighters have been trained in camps near Sabratha, which is close to the Tunisian border.
Two major attacks in Tunisia last year claimed by Islamic State - one on a Sousse resort hotel and another on a Tunis museum - were carried out by gunmen who officials said had trained in Libya.
The New York Times earlier reported that Friday's air strikes targeted a senior Tunisian operative, Noureddine Chouchane, connected to both of last year's attacks.
The mayor said officials visited the site of the strike and found weapons in the building, but he did not give any further details. Some Tunisians, a Jordanian and two women were among the dead, he said.
Several Tunisians who had recently arrived in Sabratha were among survivors.
Since Libyan leader Muammar Gaddafi was overthrown in 2011, the north African country has slipped deeper into chaos with two rival governments each backed by competing factions of former rebel brigades.
As Islamic State has expanded in Libya, taking over the city of Sirte and attacking oil ports, so too have calls increased for a swift Western response to stop the group establishing a base outside its Iraq and Syria territory.
Western officials and diplomats have said air strikes and special forces operations are possible as well as an Italian-led "security stabilisation" plan of training and advising.
U.S. and European officials insist Libyans must invite help through a united government, but say they may still carry out unilateral action if needed.
Last November the United States said it carried out an air strike on Libya's Derna to target Abu Nabil, also known as Wissam Najm Abd Zayd al Zubaydi, an Iraqi commander in Islamic State.