TRIPOLI (Reuters) - Libyan forces have found some 90 bodies of slain militants at the sites of recent U.S. air strikes near the former Islamic State stronghold of Sirte, they said in a statement on Thursday.

The forces posted pictures of desert hideouts covered with sand and grass and said the sites were being used for training. Shells, suicide belts and booby traps had been recovered there, the statement added.

They also said they had arrested two suspected militants and killed four who refused to surrender. The forces are led by brigades from the city of Misrata and ousted Islamic State from Sirte in a near seven-month campaign that ended in December.

U.S. officials have said more than 80 militants, some plotting attacks in Europe, had been killed a week ago when B-2 bombers dropped about 100 precision guided munitions on camps about 28 miles (45 km) southwest of Sirte.

They said the strikes targeted militants who had fled from Sirte. The Misrata-led forces said most of those found at the sites of the strikes were not among those who had fled from Sirte.

The forces’ statement gave no details of the militants’ nationalities or where they were thought to have been previously.

Pictures posted alongside the statement showed desert shelters covered with canvas or plastic sheeting and branches, and a hideout dug into the sand. There were also pictures of a number of several dead bodies, burnt out vehicles, weapons and satellite phones.

The statement said some 70 bodies had been found in one location and 20 bodies at another spot. It was not clear how far apart the two sites were.

Islamic State’s defeat in Sirte left the group without any territory it controlled in Libya, though it has a presence in other parts of the country.

Libyan and Western security officials have long warned that some fighters escaped from Sirte before the battle or during its early stages. Islamic State leaders have said they intend to regroup from outside Sirte.