British jubilant as Taliban leader in south Afghanistan killed in air strike

United States military says that Mullah Osmani is the highest-ranking insurgency chief to be killed

Britain and its Nato allies claimed a major victory over Taliban insurgents in southern Afghanistan yesterday as US forces reported that the Taliban's military chief in the region had been killed in an air strike.

Mullah Akhtar Mohammad Osmani, one of the Taliban's most senior leaders, with close links to Osama bin Laden, was said to have died on Tuesday in Helmand province, the scene of bitter fighting involving British troops last summer. Mullah Mohammad Omar, the Taliban's shadowy leader, who like bin Laden remains at large, declared Osmani his heir in 2001.

A US military spokesman, Colonel Tom Collins, said the Taliban leader was killed, along with two associates, when their car was destroyed on an isolated desert road. "Mullah Osmani is the highest-ranking Taliban leader that we've ever killed," he said. "His death is very significant, and will hit the Taliban's operations." He commanded the Taliban in its southern heartland, including Helmand and Kandahar provinces, during the heaviest fighting Afghanistan has seen since the Taliban and its al-Qa'ida allies were ousted from power in 2001.

Britain significantly increased its military commitment in the country earlier this year, with the deployment of 4,000 troops in Helmand. Until 2006 only two British soldiers had been killed in combat in Afghanistan, but 19 more have died in Helmand in recent months. British commanders will hope that the removal of one of the Taliban's top figures might disrupt the movement's resurgence, and weaken the spring offensive expected after the traditional lull in fighting during the Afghan winter.

The Taliban immediately denied that Mullah Osmani was dead, saying he was elsewhere in Afghanistan. A purported spokesman for the movement, Qari Yousef Ahmadi, said the air strike killed Mullah Abdul Zahir, a group commander, and three other Taliban fighters. There was no immediate confirmation from Afghan officials, or visual proof of the claim, but Col Collins said the US had withheld the news for four days while it checked intelligence and other sources to confirm the leader's identity.

"We're sure that we killed Osmani," he said. "It's a big loss for the Taliban. But the Taliban is also fairly adaptive. There is no doubt that they will put somebody else in that position, and we will go after that person too."

The spokesman added that Mullah Osmani had been "utilising both sides" of the Afghan-Pakistan border and that the US military had been tracking him for some time. "When the time was right, and we thought we had a good chance of hitting him without causing any harm to civilians, we struck."

Mullah Osmani was one of three deputies to Mullah Omar, in charge of the Taliban's finances. Ahmed Rashid, a leading expert on the movement, said his death would be the first casualty among the Taliban's top leadership in five years. Regarded as highly ideological, he was instrumental in some of the most notorious excesses of Taliban rule, such as the destruction of the ancient Buddha statues in Bamian and the trial of Christian aid workers in 2001.

During their regime, Osmani was the corps commander in Kandahar, the movement's seat of power. In June, a man claiming to be Mullah Osmani - his face was concealed by a black turban - gave an interview to a Pakistani television network in which he said Mullah Omar and Bin Laden were alive and well.