The report on Saturday by the external Pashto-language service of Iranian state radio quoted an "informed source" as saying the alleged arrest took place "some time ago", but gave no further details.
It went on to claim that US officials were keeping news of the arrest secret and were likely to announce it later in the year - in order to help US President George Bush's re-election chances in November polls.
"The capture of the al-Qaida leader was made some time ago, but Bush is intending to announce it at the time of the American presidential election," the report claimed.
The report said US Defence Secretary Donald Rumsfeld's visit to Afghanistan during the week were made to follow up on bin Ladin's alleged arrest.
"We cannot confirm it at all"
Khurshid Mahmud Kasuri,
Pakistan Foreign Minister
Meanwhile, top Pakistani officials denied the reports.
Pakistan Foreign Minister Khurshid Mahmud Kasuri told reporters at a press conference he could not confirm reports carried by "international media" that bin Laden has been arrested in Pakistan.
"We cannot confirm it at all," Kasuri said.
Pakistan's military spokesman Major General Shaukat Sultan told reporters, "This report is not correct." Foreign ministry spokesman Masud Khan also told reporters "there was no report of bin Ladin's arrest from the tribal areas of Pakistan."
Washington also rushed on Saturday to deny the alleged reports.
"I do not have any reason to think it is true," said Larry Di Rita, the chief Pentagon spokesman who travelled with Rumsfeld this week to Afghanistan.
Lt Col Bryan Hilferty, a spokesman for the US military in Afghanistan, also said he had no information to suggest bin Ladin had been caught.
"Things are going well, and we believe we will eventually catch all the leaders of al-Qaida, but I know nothing of that report," he said.