Two airstrikes carried out by US forces in Afghanistan’s southern Helmand and eastern Kunar provinces have killed at least 14 civilians, mostly children and women.

Five women and seven children were among those killed in the attacks that took place in Helmand's Gereshk and Kunar's Chawki districts on Monday and Wednesday, the UN Assistance Mission in Afghanistan (UNAMA) said Thursday.

"Civilian casualty toll from airstrikes in #Afghanistan continues to rise," UNAMA said on Twitter. "Parties must respect international obligations to protect civilians from harm."

The attacks came days after at least eight Afghan policemen were killed in a US airstrike on Helmand province On May 16.

A spokesman for US forces in Afghanistan, Colonel Dave Butler, said the aerial attack took place after Afghan forces requested US air support during a firefight with Taliban militants near the provincial capital of Lashkar Gah.

And UNAMA last week said it was probing allegations of civilian casualties following US airstrikes in Farah and Nimroz provinces.

The United States has recently stepped up its air raids in an attempt to exert pressure on the Taliban to accept a negotiated end to its 18-year insurgency.

Last month, the mission published a report saying civilians were for the first time being killed in greater numbers by US forces than by the Taliban and other militant groups.

During the first three months of 2019, US and pro-government forces were responsible for the deaths of 305 civilians, whereas insurgent groups killed 227 people, it said.

The UN mission in Afghanistan recorded 649 civilian casualties as a result of aerial attacks in the first nine months of last year, the highest number in any year since systematic recording began in 2009.

The Taliban’s five-year rule over at least three quarters of Afghanistan came to an end in the wake of a US-led invasion in 2001, but the militant group still continues to attack government and civilian targets as well as foreign forces.

The administration of US President Donald Trump is now negotiating with the Taliban group.