Airstrikes launched by the United States have hit an Islamic State group vehicle and four militant positions in Libya, raising to 48 the number of U.S. airstrikes against the extremist group since Washington launched its anti-IS campaign in Libya on Aug. 1.

In a statement Tuesday, U.S. Africa Command says it conducted the strikes in the coastal city of Sirte "at the request of, and in coordination with," Libya's United Nations-backed government.

Sirte is the Islamic State group's last remaining stronghold in the country, and Libyan troops have been forcing the militants into ever-smaller bits of territory there, backed by the U.S. airstrikes.

The U.S. says the bombing campaign is critical to protecting U.S. national security interests, by denying IS a safe haven in Libya.