Heavy fighting erupted on the outskirts of Lashkar Gah, the capital of Helmand province, after the Taliban attacked several outposts in the area.

The US "conducted several targeted strikes in Helmand" to defend Afghan troops as they came under attack, said military spokesman Colonel Sonny Leggett.

Under a deal the Taliban signed with Washington in February, the insurgents are not supposed to hit urban areas and are meant to keep violence down.

The US committed to pulling all foreign troops from the country by next May in return for Taliban security pledges and an agreement to begin talks with the Afghan government in Qatar.

General Scott Miller, the head of the American military deployment, warned the Taliban to "immediately stop their offensive actions in Helmand Province and reduce their violence around the country".

"It is not consistent with the US-Taliban agreement and undermines the ongoing Afghan Peace Talks," Miller said in a statement.

While the Taliban have largely held back from launching major attacks on Afghan cities, they have stepped up attacks against Afghan troops.

Helmand, which along with neighbouring Kandahar province is considered a Taliban stronghold, is where international forces fought some of the bloodiest campaigns of Afghanistan's 19-year war.

US troops are still stationed in the province but in much smaller numbers than previous years.

President Donald Trump last week said that all American soldiers "should" be home by Christmas, in a surprise announcement that if acted upon would dramatically speed up the timeline for ending America's longest conflict.