LONDON — Britain confirmed Sunday it briefly sent troops back to a bloody district of Helmand Province to assist Afghan forces, raising further questions about Afghan readiness to maintain security after NATO forces withdraw.

The Ministry of Defense said 80 British military advisers traveled back to Sangin district this month to assist 2,000 Afghan soldiers with an eight-day operation to clear Taliban insurgents.

More than 100 British troops died in Sangin during several years of operations there, and U.K. forces handed off control of the district in 2010.

Because the mission involved sending troops outside of their usual area of operations, it required special permission from Defense Secretary Philip Hammond.

The defense ministry downplayed the U.K. involvement, saying its troops "do on occasion" operate outside their usual area in central Helmand.

"Such out of area operations have been a long standing element of the U.K. mission in Afghanistan and are not an indication of a deteriorating security situation in any particular area," it said in a statement. "The concept is neither new nor novel."

It said the advisers from 4th Battalion the rifles lent tactical support to soldiers from the Afghan National Army's 3/215 Brigade, acting "purely in an advisory role" for a specific operation to restore security in the area.

The operation was "in line with" British forces' current role of providing training, advice and assistance to Afghan forces, the defense ministry added.

Still, it was the first time since the international military coalition handed over lead responsibility to Afghan forces last month that foreign troops offered so much reinforcement.

The Ministry of Defense confirmed that a number of insurgents were killed in the operation, but was not able to offer exact figures.

The Sunday Times newspaper — which first reported the operation — put the number at 12, and said two Afghan soldiers had died.

The newspaper said it had learned of the operation earlier this month but agreed at the Ministry of Defense's request not to publish any details until troops were safely back at Camp Bastion, their base in southern Afghanistan's Helmand Province.

Insurgents have been increasing attacks in Helmand Province, emboldened by the withdrawal of foreign forces from the area.

By the end of the year, NATO forces in Afghanistan will be halved. At the end of 2014, all combat troops will have left and will be replaced, if approved by the Afghan government, by a much smaller force that will only train and advise the Afghans.