TRIPOLI, Libya (Reuters) - Islamic State said it had carried out two suicide bombings against brigades loyal to Libya's U.N.-backed unity government, inflicting heavy casualties during fighting west of the militant group's stronghold of Sirte.
The brigades said 32 of their men had been killed and 50 wounded as they pushed Islamic State fighters back towards Sirte on Wednesday, their heaviest losses for months.
Western powers are counting on the new government to unify Libya's political and armed factions to take on Islamic State.
The militant group took advantage of Libya's political turmoil and security vacuum to take over Sirte last year and establish a presence in several other Libyan towns and cities.
It controls a strip of coast about 250 km (155 miles) long either side of Sirte.
The ultra-hardline group said in a statement released overnight that a Sudanese militant had carried out a truck bombing on the road between Bani Walid and Sirte, targeting a group of brigade fighters.
A second bomber struck at Buayrat al-Hasun, about 90 km west of Sirte, the statement said. It said 26 "apostates" had been killed in the two operations and 30 wounded.
Military officials said on Wednesday seven of their men had been killed in the bombing at Buayrat al-Hasun.
The fighting comes after Islamic State militants overran the town of Abu Grain and several villages after staging suicide attacks against checkpoints in the area on May 5.
The unity government then created a new operations room in Misrata, which announced a campaign to recapture Sirte.
Abu Grain is about 140 km west of Sirte and about 100 km south of Misrata.
The unity government arrived in Tripoli in late March and is still trying to establish its authority. It has been supported by Misrata's powerful military brigades, which also have a strong presence in the capital. But it has so far failed to win formal backing from key political and military factions based in eastern Libya.
(Writing by Aidan Lewis; Editing by Janet Lawrence)