KABUL, Afghanistan — American airstrikes hit Taliban positions in an embattled district of Helmand Province in southern Afghanistan on Tuesday after the militants tunneled under an army post and set off explosives, causing heavy casualties, Afghan officials said.

The toll from the explosions that rocked army posts in the town center of the Sangin district, which has been the scene of intense fighting for two days, was not immediately clear. Afghan officials said 10 to more than 20 soldiers had been killed, with many others unaccounted for. A Defense Ministry official, however, played down those numbers.

Brig. Gen. Charles H. Cleveland, a spokesman for American forces in Afghanistan, said the United States military had carried out approximately 10 airstrikes in and around the town of Sangin, where Helmand’s main market and seat of government are, in the past 24 hours. “We are continuing to focus closely on Sangin, and Helmand at large, to help our Afghan partners,” General Cleveland said.

Shakil Ahmad, a spokesman for the Afghan Army’s 215 Maiwand Corps in Helmand, put the toll at 10 killed and six wounded. Other officials said the number of deaths was at least twice that.