KABUL, Afghanistan — Taliban insurgents and Afghan government forces battled for control of the key southeastern city of Ghazni on Friday, with both sides claiming victory at the end of the day without any independent confirmation.

If the Taliban takeover is confirmed, such a rout would be the insurgents’ most important strategic gain in years. If it falters, it will be evidence once again that the insurgents can do serious damage but cannot take and hold territory.

Local witnesses and health officials feared the casualty toll would be high. Zahir Shah Nikmal, head of the provincial department of public health, said 16 bodies and 40 wounded people had been brought to hospitals so far. Almost all were members of the security forces, he said, and officials were trying to arrange evacuations by helicopter for the critically wounded.

The American military said it had sent helicopters to support Afghan troops in Ghazni, and that it had carried out one airstrike, using a drone.