Taliban fighters seized most of the capital of northern Afghanistan’s key Kunduz province on Sunday, and took another neighbouring provincial capital after a monthlong siege.

The advances were the latest in a series of blows to government forces as US troops complete their pull-out after nearly two decades in the country.

The militiamen planted their flag in the main square of Kunduz city, where it was seen flying atop a traffic police booth, a video obtained by the Associated Press showed.

Provincial council member Ghulam Rabani said fighting between insurgents and government forces had taken place around the governor’s office and police headquarters in Kunduz city but the Taliban had later taken over the two buildings. They also have control of the main prison building, he added.

Afghans inspect a damaged building after air strikes in Lashkar Gah (Abdul Khaliq/AP)

Another provincial council member from Kunduz, Mohammad Yusouf Ayubi, also said Afghan forces only control the airport and main army barracks, and that the Taliban control the rest of the city.

Kunduz is a strategic crossroads with good access to much of northern Afghanistan as well as the capital, Kabul, about 200 miles (335km) away.

With Taliban attacks increasing, Afghan security forces and government troops have retaliated with air strikes aided by the United States. The fighting has raised growing concerns about civilian casualties.

On Saturday, Taliban fighters entered the capital of Jawzjan province after sweeping through nine of 10 districts in the province. Several other of the country’s 34 provincial capitals are threatened as Taliban fighters sweep through large swathes of Afghanistan at a surprising speed.

Meanwhile, air strikes damaged a health clinic and high school in the capital of southern Afghanistan’s Helmand province, a provincial council member said on Sunday.

A Defence Ministry statement confirmed that air strikes were carried out in parts of the city of Lashkar Gah. It said forces targeted Taliban positions, killing 54 fighters and wounding 23 others, but made no mention of a clinic or school being bombed.

Damage to a school in Lashkar Gah (Abdul Khaliq/AP)

Majid Akhund, deputy chairman of the Helmand provincial council, said air strikes hit a health clinic and a school in the city’s 7th police district late on Saturday, but he said the area is under Taliban control so any casualties could have been caused by the Taliban there.

Also on Sunday, the Taliban forces overran Taleqan, the capital of Takhar province which lies next to Kunduz, two provincial officials said.

Takhar has particular significance for the anti-Taliban northern alliance fighters who joined the US-led coalition to oust the religious militia in 2001.

Sayed Sharafuddin Aini, a politician from Takhar province, said the Taliban managed to take the city in the afternoon after three months of siege during which it took control of all of the province’s countryside.

Nazifa Yousefi Beg said that all provincial officials including the governor, provincial police chief, and provincial council members have been captured in Taleqan.

She said she feared for their fates in Taliban hands and urged the government to send troops to retake the city.

Debris at a clinic damaged by the air strikes (Abdul Khaliq/AP)

Dr Ahmad Khan Weyar, an official from the Helmand public health department, said a nurse was killed when an air strike hit a health clinic, and a guard was injured.

“American invaders bombed and destroyed another hospital and school in Helmand,” the Taliban said in a statement. It said Safyano Hospital and Muhammad Anwar Khan high school were bombed.

The clinic in Lashkar Gah was offering services mostly to nomads who were passing through the area, according to Mr Akhund, but in recent days the area was under Taliban control and Taliban may have been treated there.

Heavy fighting has taken place in and around Lashkar Gah and both US and Afghan government air forces have carried out air strikes in the city. The Taliban control nine of the city’s 10 police districts.