MOGADISHU, Somalia -- Heavily armed al-Shabab extremists have stormed a military base in Somalia's semiautonomous 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-Shabab and the growing presence of fighters linked to the Islamic State of Iraq and Syria (ISIS).

The attack began with a blast at the remote Af-Urur camp, roughly 62 miles 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.

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

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

Puntland in northern Somalia also faces a growing threat from ISIS-linked fighters who have split from al-Shabab, which grew out of the Horn of Africa country's quarter-century of chaos.

Al-Shabab last year became the deadliest Islamic extremist group in Africa, with more than 4,200 people killed in 2016, according to the Washington-based Africa Center for Strategic Studies.

The extremist group recently vowed to step up its attacks after the federal government announced a new offensive against it. Targets have included high-profile spots like military facilities, hotels and areas close to the presidential palace.

Somalia's military is under growing pressure to assume more responsibility for the country's security as a 22,000-string multinational African Union force plans to start withdrawing next year.

The prospect of a security vacuum has concerned the international community. Somalia's president has urged that the United Nations arms embargo on his country be lifted soon, saying the military needs more than AK-47s to combat al-Shabab and the ISIS-linked fighters.

President Mohamed Abdullahi Mohamed, a Somali-American who was elected in February, has repeatedly said al-Shabab can be defeated within two years, but he warns that could take much longer without a better-equipped national military.