BANI WALID, Libya — Libya’s government declared Wednesday that it had taken control of one of the last strongholds of deposed dictator Moammar Khadafy’s loyalists, as its fighters in the heart of the city fired their guns into the air to celebrate victory after fierce battles that left dozens dead and thousands displaced.

The capture of Bani Walid, some 90 miles southeast of Tripoli, was a triumph for the government that replaced Khadafy’s regime. But the length of time it took the government to secure the town — a full year — underlined the difficulties the new regime faces in imposing its authority over squabbling tribes and heavily armed militias.