US and Afghan forces came under attack in eastern Afghanistan on Saturday, officials said in Kabul, as they launched investigations into what the New York Times described as a deadly shootout between Afghan and American soldiers during a joint exercise.
The Times, quoting two Afghan officials, reported that five or six American soldiers and six Afghan soldiers were killed. The newspaper quoted a US military official saying there were at least six American casualties and confirmed that there were fatalities without saying how many.
US officials, speaking on the condition of anonymity, told Reuters, that based on initial information, there were multiple American casualties in the incident.
Mubariz Khadem, a senior security official in Nangarhar province, where the incident occurred, told Reuters on Saturday that clashes took place between US and Afghan forces and casualties were feared.
Insider attacks, often known as "green-on-blue" attacks, have been a regular feature of the conflict in Afghanistan, although their frequency has diminished in recent years.
Still, details around the incident on Saturday remain confused with a senior Afghan defense official also telling Reuters that it was not clear whether the incident was a result of clashes between Afghan and foreign forces or whether hardline Islamist militants were responsible for the attack.
"We are not ruling any possibility out but we are not calling it an insider attack, Taliban attack, or 'green-on-blue' at this stage," said the official who requested anonymity.
Colonel Sonny Leggett, a spokesman for US forces in Afghanistan, said a combined US and Afghan force conducting an operation in Nangarhar was engaged by direct fire.
"We are assessing the situation and will provide further updates as they become available," he said.
Taliban sources were not immediately available to comment.
Sohrab Qaderi, a provincial council member in Nangarhar, said clashes happened between the Afghan army and foreign forces in Shirzad district on Saturday afternoon.
He said members of the Afghan forces had been operating in the area since last month, and foreign forces were also in the district to defend against Taliban attacks.
"It seems that clashes happened between Afghan and foreign forces during a raid or maybe there was a tactical mistake," said Qaderi.
Investigations of past rogue attacks had uncovered many reasons for "green-on-blue" shootings, including frustration with the 18-year-old war in Afghanistan against the Taliban and other hardline Islamist groups.
About 14,000 US troops are stationed in Afghanistan as part of the US-led NATO mission to train, assist and advise Afghan forces and to carry out counter-terrorism operations.
US diplomats have been talking with the Taliban for months to agree a timetable for the withdrawal of foreign forces in exchange for security guarantees.
Despite talks between the United States and the Taliban to end the war, violence in the country has not ebbed.