JALALABAD, Afghanistan — The American military bombed members of an Afghan government militia who were on the front lines of the battle against the Islamic State in eastern Afghanistan, killing at least 13 fighters after at least one opened fire on American Special Forces soldiers deployed there, Afghan officials said Thursday.
While some Afghan officials said that at least two American soldiers were killed in what was described as an insider attack by friendly forces, Capt. Tom Gresback, a spokesman for the United States military in Afghanistan, rejected those reports and said that only one American service member had been wounded.
Captain Gresback would not say whether the service member had been wounded by friendly fire, or whether the United States had bombed the militia afterward.
The episode unfolded in the Achin district of Nangarhar Province, the stronghold of the Islamic State’s affiliate in Afghanistan. Over the past year, Afghan forces, with the help of American Special Forces units and airpower, have tried to wipe out the group there, but it has been an uphill task because the Afghan government has had little control in the area for many years. Every time the Islamic State has been squeezed in Achin, the fighters have shifted to a neighboring district.
Nangarhar has been the deadliest province for American forces in the past year, even as the size of the American presence in the country has been reduced to about 14,000 troops. Eight American service members have been killed in the province over the past nine months.
Attaullah Khogyani, a spokesman for the governor of Nangarhar Province, said local militiamen fighting on behalf of the government had gotten into a verbal clash with the Americans before a shootout erupted.
“There was a bombardment also,” Mr. Khogyani said. “I don’t have exact information on casualties.”
Mohammed Ismail Shinwari, the district governor of Achin, said 13 to 15 militiamen were killed in the confrontation.
Members of the provincial council said the militia was led by a member of the Afghan Parliament and a regional strongman, Zaher Qadir, and had possibly been infiltrated by the Taliban.
“There was a new fighter that had joined the group, and he was the one who opened fire on the Americans,” said Khair Mohammed, a commander in Mr. Qadir’s militia.
Two years ago, Mr. Qadir’s militia decapitated four members of the Islamic State, also known as ISIS, in what they said was an act of retaliation, and then circulated on social media pictures of the heads placed on piles of rocks on the side of a road.
In southern Afghanistan, at least five police officers were killed and two civilians were wounded during a Taliban attack in the Naw district of Helmand Province. The Taliban overran a check post in the Surkhgulf area of the district, said Bashir Ahmad Shakir, a member of the provincial council.
But there was also some better news in the south.
Officials in Kandahar Province said they had completed a polio vaccination campaign in Shah Wali Kot, a district that last year reported the most polio cases in the world. As a measure of the gravity of the problem in the region, a fifth polio case within the past year was recently confirmed in the district: Ashrafia, a 2 ½-year-old girl, tested positive about two weeks ago and died soon after because of the severity of the virus.
Afghanistan is one of only three countries in the world reporting polio cases. Last month, the United Nations appealed to all sides in the conflict to allow polio workers to conduct the first of three vaccination campaigns in Shah Wali Kot. Although the campaign got off to a rocky start, with the Taliban restricting access and government forces reportedly burning a health center and arresting a vaccinator, officials announced that they had managed to complete the first phase.
“I am grateful to the authorities and community leaders who enabled 503 frontline workers to conduct the first campaign this week,” Toby Lanzer, the United Nations humanitarian coordinator in Afghanistan, said in a statement on Wednesday.
Dr. Sardar Wali, the senior health official in Shah Wali Kot, said the United Nations appeal and attention from the news media, including The New York Times, had compelled the governor to mobilize his staff members to take urgent action.
“The W.H.O. and Unicef representative met the Taliban in Shah Wali Kot after The New York Times report, and the governor summoned district authorities and elders and warned them to work hard in order to convince the Taliban through elders to allow the campaigners to carry out the polio drive in those blocked regions,” Dr. Wali said. “The Taliban agreed to allow the polio campaign in those 14 restricted regions, and it has been done.”