Heavily armed Al-Shabaab militants have stormed a military base in Somalia's semi-autonomous state of Puntland, killing close to 70 people and wounding dozens more, officials said Thursday.

Residents said civilians, including women, were beheaded during the rampage.

Officials called it the region's deadliest attack in years, highlighting the twin challenges facing security forces from the Al Qaeda-linked Al Shabaab and the growing presence of fighters linked to the militant Islamic State group.

The attack began with a blast at the remote Af-Urur camp, roughly 100 kilometres west of the commercial hub of Bossaso, before the extremists overran the base and killed soldiers at close range, said Ahmed Mohamed, a senior military official.

Close to 70 people were killed, though an exact death toll was not yet available, Mohamed said. Abdi Hersi Ali, Puntland's interior minister, said troops suffered causalities but he declined to give further details.

Residents in the area reported chaotic scenes, with fighters beheading several civilians they encountered.

One witness, Abdibasit Hassan, said women were among those beheaded. “The situation is grim over there. This attack was an unexpected one,” Mohamed said. The extremists, including suicide bombers, reportedly attacked the base from three directions, forcing soldiers to retreat.

Col Hashi Ahmed, a senior military official, told The Associated Press that reinforcement troops reached the area and drove the extremists out of the camp. He estimated that at least 100 fighters were involved in the attack.

Al Shabaab claimed killing at least 61 soldiers in the attack. The Search for International Terrorist Entities (SITE) Intelligence Group, which monitors extremist groups, said the extremist group issued the claim via its Shahada News Agency. Al Shabaab also said it seized a large amount of weapons and ammunition and more than a dozen military vehicles.

Puntland in northern Somalia also faces a growing threat from IS-linked fighters who have split from Al-Shabaab.

Liban Mohamed, a nurse at the hospital in nearby Armo town, said at least 40 wounded soldiers had been brought there after Thursday's attack.