British forces killed an alleged Taliban leader in southern Afghanistan, U.K. and Afghan officials said Tuesday, in what they claimed was a major victory against the insurgency there.

Mullah Mansur was killed Monday in a strike by helicopters in Helmand province, the British defense ministry said.

Helmand government spokesman Daoud Ahmadi said Mansur was the aviation minister in the Taliban regime that was ousted by the U.S.-led invasion in 2001.

British military spokesman Lt. Col Nick Richardson said Mansur was "one of the most dangerous men in Helmand."

"The attacks he helped plan and execute have probably killed or wounded hundreds of people, and most of them have been either Afghan civilians or police," he said, adding his death was a "serious blow" to the insurgency.

Helmand is a stronghold of the Taliban and the most violent region of Afghanistan.

Insurgent attacks in Afghanistan are running at record levels eight years after the U.S. invasion and the central government has little authority outside the capital, Kabul. President Barack Obama has ordered an extra 21,000 troops to the country to turn the deteriorating situation around.