KANDAHAR, Afghanistan — In a bloody overnight attack in Kandahar Province in Afghanistan on Wednesday, the Taliban routed an Afghan Army outpost, killing dozens of soldiers and raising fears of a concerted insurgent offensive in the province, a former seat of Taliban power that took years of effort by coalition and Afghan forces to secure.

The attack happened in Khakrez District, about 30 miles from Kandahar city, and a large number of casualties has raised concerns about new Taliban tactics against an Afghan force already losing men in record numbers.

One senior security official said 39 Afghan Army soldiers were killed in the attack, which began at 10 p.m. on Tuesday and lasted for three hours. The official said that 17 other soldiers were wounded and that a dozen more had not been accounted for.

The Afghan government’s media and information centre said 26 soldiers were killed and 13 others wounded. Army officials in Kandahar confirmed the attack but would not provide details of casualties.

Mohammed Yousuf Younusi, a member of Kandahar’s provincial council, described the episode as “a massacre” and said there was prior intelligence that the Taliban would attack in large numbers.

“The Taliban fooled the officials — they split into three groups, and launched simultaneous attacks,” Mr Younusi said. “One group attacked Shah Wali Kot District, another attacked Nish District, and a third group attacked this Afghan Army base, which is not far from the district centre. Things are really bad, and this is a shame.”

Kandahar was the original seat of the Taliban government when it controlled Afghanistan from the mid-1990s until its ouster by the United States invasion in 2001. More than 550 NATO coalition troops have died in the province, and it became relatively secure only after a strong push during President Barack Obama’s troop surge starting in 2010.

The gains in Kandahar have been solidified in recent years by a strongman police chief, Gen. Abdul Raziq, a favourite of American commanders who has also been accused of abuses by human rights groups.

The province’s dependence on one individual for security — with no Plan B and at the cost of reforming the police as an accountable force — has long worried diplomats and Afghan officials.

The Taliban have steadily been making gains in surrounding provinces, but in Kandahar, General Raziq’s forces have long been successful in keeping the insurgents at bay. But the general’s control is being tested by this new wave of attacks.

In recent weeks, in addition to firing on security outposts in most of the province’s districts, the Taliban have also carried out heavier assaults and ambushes in at least six districts, often inflicting casualties on Afghan forces.

“For the last two weeks, the Taliban have been attacking the northern districts of Kandahar and have killed many Afghan security forces,” said Noor Nawaz Piawari, a military analyst in Kandahar. “The northern districts are close to Helmand and Uruzgan, which they control in large parts. They are after expanding their territory to create routes that connect to Pakistan,” where most of the insurgency’s leadership is based.

Mr Piawari said General Raziq would struggle to maintain security as his police forces are stretched and face casualties, with the Taliban often attacking isolated outposts across several districts.

For an Afghan force that lost men in record numbers last year, the past month has proved particularly deadly. The Taliban have overrun three districts across the country in the last week, and the pattern suggests they are focused on inflicting heavy casualties on Afghan forces, rather than holding the territory they take over. When they overrun outposts and police stations, they often capture even more weapons and ammunition, most of it paid for by the United States and its allies to help bolster the Afghan forces.

Both in Janikhel District of Paktia Province and in Kohistan District of Faryab Province, the Taliban looted all the weapons and equipment left behind by the Afghan forces. In Taiwara District, in western Ghor Province, the Taliban killed as many as 30 government forces.

When Afghan forces took back the district centre of Kohistan on Tuesday, they estimated that the Taliban had seized some 40,000 rounds of machine gun ammunition, a mortar with 20 rounds and 30 rocket-propelled grenades, according to Sulaiman Rahmani, a militia commander in the district. The province’s police chief, however, said that whatever the Taliban took had been bombed by the Afghan Air Force.

After overrunning the district centre of Janikhel, and seizing four pickup trucks, one Humvee and whatever weapons they could get their hands on, the Taliban withdrew again, officials there said.

“They have taken position in the mountains above the district centre to strike on the Afghan forces, in case they plan to move ahead to retake the district,” said Shakeela Mangal, a member of the Paktia provincial council.