Disguised in army uniforms, a group of Taliban insurgents stormed an army base in Afghanistan’s most secure northern Balkh province Friday, killing several dozen soldiers in one of the bloodiest such attacks in years, officials said.

There were conflicting reports as to how the guerrillas made their way inside the vast, heavily fortified base, with some reports saying they managed to enter the compound of the 209 Corps by joining a convoy of military vehicles returning to the base from a restive neighboring province.

An army spokesman for the region, Qahar Aram, gave a different account in a phone interview. He said one of the bombers detonated a vehicle laden with explosives at the main entrance of the base, paving the way for as many as nine insurgents to rush inside.

From the gate, they headed to a dining facility and a mosque, he said.