TRIPOLI, Libya – Gunmen ambushed a Libyan bank van and made away with over $50 million on a highway east of Tripoli, officials said Tuesday. The brazen heist underscores the weakness of the central government in the North African country, where authorities are struggling to control unruly militias.

A security official told the Associated Press that the Central Bank van had no guards accompanying it when was ambushed near the city of Sirte late Monday. The official news agency LANA, quoting a bank official who was with the van, said that a single carload of guards was escorting the money on its way from Sirte’s airport to the local bank branch, but they were unable to resist the 10 attackers.

LANA quoted Col. Khaled al-Akari, a security official in Sirte, as saying troops had closed the entries and exits of the city to try to apprehend the thieves. Sirte was a main support base for longtime dictator Moammar Gadhafi, and he made his final stand there before he was captured and killed in 2011.