KABUL, Afghanistan — A brazen and bloody overnight assault Friday by the Taliban on a key provincial capital in central Afghanistan has increased pressure on U.S.-backed Afghan forces that are withering under relentless attacks, prompting President Ashraf Ghani to call an emergency meeting of his security officials.

While government security forces in the city of Ghazni repulsed the multipronged attack with the help of U.S. air support, Taliban insurgents remain hunkered down on its outskirts, and some were still holed up in residential areas, according to Interior Ministry deputy spokesman Nasrat Rahimi.

At least 39 insurgents were killed, while 14 police died and 20 were wounded in the fighting, said provincial Police Chief Farid Ahmad Mashal. He said the bodies of the Taliban fighters were found under a bridge in the southern part of Ghazni.

Mashal said there were more than 100 other casualties but could not give a breakdown of the dead and wounded.

Among the injured were four Afghan troops who were hurt when their helicopter crash-landed during the fighting, said Defense Ministry spokesman Mohammad Radmanish.

The Taliban claimed to have shot it down, Radmanish said it was not clear if the aircraft had been hit or crash-landed for other reasons.

The city of about 140,000 people was in lockdown as residents stayed indoors and reported sporadic gunfire. All shops were closed, they said, as was the highway from the capital of Kabul to Afghanistan’s southern provinces that runs through Ghazni.

Taliban fighters set fire to the local TV building and also destroyed the telecommunications tower, located just outside the city, cutting all cellphone and land line access to Ghazni, said Ali Akbar Kasemi, a lawmaker from the city.

City hospital administrator Baz Mohammad Hemat said two wounded civilians were brought in for treatment. He feared that there were more wounded who could not make it to the hospital because the city was shut down and ambulances were being sent out.