Late on Saturday, however, Al Jazeera's correspondent in Islamabad confirmed quoting sources close to the Afghan Taliban movement that a US air strike in Helmand on December 19 had killed Osmani; Mawalawi Abd al-Dhahir Balushi, his bodyguard; and another unidentified person.
Earlier in the day, Mullah Hayat Khan, a Taliban commander, told Reuters: "We strongly deny this. He is not present in the area where American forces are claiming to have killed him.
"The American and Nato forces from time to time make such false claims. It's just propaganda against the Taliban."
Tom Collins, a military spokesman, described Osmani as part of a group of "co-equals" at the top of the Taliban leadership and a close-associate of Osama Bin Laden and Mullah Omar, the Taliban leader.
In June, a man claiming to be Osmani gave an
interview to a Pakistan TV channel
"This guy had been deeply involved in terrorist acts against the people of Afghanistan, Nato and the government," Collins said.
"He was a top commander of Taliban operations in the south and now he's no more."
Osmani was also in charge of the Taliban's finances and was involved in roadside bombs, suicide attacks and kidnappings, Collins added.
Collins said Osmani had been utilising both sides of the Afghan-Pakistan border, and that the US military had been tracking him for a while.
"When the time was right, and we thought we had a good chance of hitting him without causing any harm to civilians, we struck," he said.
Although the US said Osmani was an associate of bin Laden, Omar and Afghan anti-government commander Gulbuddin Hekmatyar, Collins said he did not know the last time Osmani had contact with any of the three.