By Sardar Razmal

KUNDUZ, Afghanistan (Reuters) – Two American service members were killed fighting the Taliban near the northern city of Kunduz on Thursday, the U.S. military said amid reports that air strikes called in to protect the troops had caused heavy civilian casualties.

Although the U.S. military gave no details, Afghan officials said there had been heavy fighting overnight about 5 km (3 miles) from the city center, which Taliban fighters succeeded in entering as recently as last month, and air strikes had caused many casualties.

There were angry protests by civilians who brought the bodies of at least 16 dead into Kunduz, Mafuzullah Akbari, a police spokesman said. Some reports put the death toll higher but there was no immediate official confirmation.

“The service members came under fire during a train, advise and assist mission with our Afghan partners to clear a Taliban position and disrupt the group’s operations in Kunduz district,” the U.S. military said in a statement.

In a separate statement, the NATO-led Resolute Support mission confirmed that air strikes had been carried out in Kunduz to defend “friendly forces under fire”.

“All civilian casualty claims will be investigated,” it said.

In a statement, the Taliban said American forces were involved in a raid to capture three militant fighters when they came under heavy fire. An air strike hit the village where the fighting was taking place, killing many civilians.

The deaths underline the precarious security situation around Kunduz, which Taliban fighters came close to over-running last month, a year after they briefly captured the city in their biggest success in the 15-year long war.

While the city itself was secured, the insurgents control large areas of the surrounding province.

The U.S. military gave no details on the identity of the two personnel who were killed or what units they served with and there was no immediate detailed comment on the circumstances of their deaths.

Although U.S. combat operations against the Taliban largely ended in 2014, special forces units have been repeatedly engaged in fighting while providing assistance to Afghan troops.

Masoom Hashemi, deputy police chief in Kunduz province, said police were investigating to try to determine if any of the dead were linked to the Taliban.

Thousands of U.S. soldiers remain in Afghanistan as part of the NATO-led Resolute Support training and assistance mission and a separate counterterrorism mission.

The deaths come a month after another U.S. service member was killed on an operation against Islamic State fighters in the eastern province of Nangarhar.

Afghan forces, fighting largely on their own since the end of the international combat mission, have suffered thousands of casualties, with more than 5,500 killed in the first eight months of 2016.

(Additional reporting by Hamid Shalizi; Writing by James Mackenzie; Editing by Simon Cameron-Moore, Robert Birsel)