CAIRO (Reuters) - Libyan Islamist group Ansar al-Sharia, a group linked to Al-Qaeda, is formally dissolving itself, it said in a statement on Saturday.

The group, which Washington says was behind the 2012 Benghazi attack that killed the U.S. ambassador Christopher Stevens, had been at war with Khalifa Haftar’s eastern-based Libyan National Army.

The group said its decision came on the back of heavy losses that have wiped out its leadership and decimated its fighters, according to the statement.

Forces aligned with the Libyan National Army have skirmished since late last year with opponents aligned with a U.N.-backed Government of National Accord (GNA) in Tripoli.

Groups such as Ansar al-Sharia, which had tried to maintain a stronghold in the country’s east, have inserted themselves into the larger war, creating a fractious battleground overlaid by a multitude of militias.

The group’s statement called on revolutionary forces and shoura councils in Benghazi to unite in order to form a united front.