At least 18 people have been killed in a suspected US drone attack in Afghanistan. The air strike targeted militants from the Islamic State (Isis/Daesh) terror group, but some civilians are believed to have also been hit, Afghan officials said.

The attack, which took place in Nangarhar province – on the border with Pakistan – killed 15 militants and possibly three civilians.

"They were in a house to visit someone who had just come from the Hajj pilgrimage. A drone targeted the house and killed most of them," Mohammed Ali, police chief of Achin district, was quoted by Reuters news agency as saying.

However, Provincial police spokesperson Hazrat Hussain Mashriqiwal denied civilians were targeted in the strike.

Brigadier General Charles Cleveland, spokesman for the US military command in Afghanistan's capital Kabul, confirmed US forces carried out a "counter-terrorism" air strike in Achin. However, he did not discuss details of the operation.

"US Forces – Afghanistan takes all allegations of civilian casualties very seriously," Cleveland said. "We are aware of some claims of Afghan casualties, and are currently reviewing all materials related to this strike. We are continuing to look into these allegations."

US troops have been fighting against members of the Taliban, the Islamic fundamentalist movement that has waged war against the Afghani government, since 2001. The American contingent has also been conducting attacks against IS fighters in the country.

IS, which controls large swathes of Syria and Iraq, has gained hundreds of followers in Afghanistan and Pakistan and holds some territory in Nangarhar, with Achin as a stronghold.

US airstrikes and civilian casualties

This is not the first time that US forces have been accused of killing civilians during strikes against militants.

In October 2015, a US strike hit a Medicines Sans Frontieres (MSF - Doctors Without Borders) hospital in the northern city of Kunduz, killing 42 people and injuring 30. MSF accused the US of a war crime and 16 US soldiers were disciplined.

A US military enquiry labelled the attack as "human error". MSF, however, requested an independent investigation into the attack by the International Humanitarian Fact Finding Commission.

In July, the White House released a report on civilians killed in drone attacks and air strikes. The report claimed between 64 and 116 civilians had been killed from 2009 up until 2015 .

Some rights groups, however, disputed the findings, claiming the death toll of civilians killed in drone strikes was higher.