Forces loyal to Libya’s unity government said Sunday they had seized a building used by Daesh (ISIS) to manufacture explosives in its coastal stronghold.The bomb factory is the largest to be captured by fighters allied with the Tripoli-based Government of National Accord since they launched an operation to retake Sirte in May, the forces said on Facebook.

They said the building was in the southeast of Sirte, the hometown of slain dictator Moammar Gadhafi, which Daesh has controlled since June 2015.

The pro-GNA forces shared images of the building including several rooms containing explosive devices, cables and mobile phones.

The fall of Sirte, 450 kilometers east of Tripoli, would be a major blow to Daesh, which has faced a series of setbacks in Syria and Iraq.

The two-month battle for Sirte has killed around 280 pro-government fighters and wounded more than 1,500, according to medical sources at the unity forces’ command center.

The pro-GNA forces are mostly made up of militias from western Libya established during the 2011 revolt that overthrew Gadhafi.

A militia set up to guard the country’s main oil facilities has also been advancing on Daesh.

The GNA was the result of a U.N.-brokered power-sharing agreement struck in December, but it has yet to be endorsed by Libya’s elected parliament based in the country’s far east.

In other developments, the Libyan government summoned the French ambassador amid concern over the French military presence in the country.

Three French officers were killed last week in eastern Libya, and the French government acknowledged that special forces are operating there as part of Western efforts to support the unity government.

Ambassador Antoine Sivan, who is based in neighboring Tunisia for security reasons, is expected to go to Libya in the coming days to answer the summons, according to a French diplomatic official.

The official said Sunday France is focused on supporting the unity government, and encouraging Libyan forces to work together to fight extremists. The official was not authorized to be publicly named.