AC-130 gunships took part in the attack
Both accounts speak of heavy casualties.
The Pentagon says AC-130 gunships and fighter jets launched from US aircraft carriers attacked the convoy near the town of Khost, south-west of Tora Bora, the former al-Qaeda stronghold.
A compound from which the convoy of 10 to 12 vehicles had
departed was also said to have been hit.
"There were a lot of people killed and a lot of vehicles damaged or destroyed," US Defence Secretary Donald Rumsfeld told a news conference in Washington.
A Pentagon spokesman said intelligence reports had indicated that the convoy contained "leadership" but did not specify whether they were leaders of the ousted Taleban regime or al-Qaeda.
In other developments:
The Pakistan-based Afghan Islamic Press (AIP), which is generally sympathetic to the Taleban, reported that 65 people were killed in the attack.
Many others were injured when the warplanes attacked, it said.
Several Afghan elders, tribal chiefs and commanders were among the victims of the killings," Sayed Yaqeen, an official of the Paktia tribal council, was quoted as saying.
BBC Washington correspondent Stephen Sackur says that if this version of events proves to be true, it will represent a severe embarrassment for the Pentagon.
Fourteen vehicles in the convoy were totally destroyed and, according to one source quoted in the report, the victims included a militia commander, Mohammadi Ibrahim, brother of the Afghan commander Maulvi Jalaluddin Haqqani.
A member of the local government, or shura, in the region told the BBC that 15 people had been killed in the bombing.
Cave-busting bomb
It is also being reported that more than 20 civilians were killed when US aircraft bombed the village of Sarkando in the same province.
A number of others were reportedly wounded in the attack in which the village was said to have been destroyed.
Mr Rumsfeld has said that significant numbers of coalition troops will be sent into the Tora Bora cave complex as the search for Bin Laden, the man suspected of masterminding the 11 September terror attacks on the US, continues.
Anti-Taleban Afghan forces took the complex last week and have so far taken the lead in neutralising pockets of resistance and hunting for evidence.
Meanwhile, the US is sending a new bomb to Afghanistan that uses a delayed, high-pressure explosion to suck the air out of caves and tunnels.
Under Secretary of Defence Edward Aldridge said the laser-guided "thermobaric" bomb, recently tested in Nevada, "is something we clearly have a need for in Afghanistan and they're on their way over there".