The commander, named as Mullah Nangyalay, was killed in Shindand district, close to the border with Iran, said Herat provincial governor's spokesman Jailani Farhad.

Nangyalay split from the main branch of the Taliban after the 2013 death of founder Mullah Omar and joined a smaller breakaway faction led by a commander known as Mullah Rasool.

A senior provincial police source said the airstrike had been carried out by a US drone.

Resolute Support, NATO's mission in Afghanistan, told AFP their forces had launched "a defensive air strike in support of Afghan forces", with a spokesman confirming US participation in the operation.

The main Taliban group has been negotiating with Washington for more than a year over the withdrawal of US troops in exchange for security guarantees from the militants that could pave the way to intra-Afghan peace talks.