Unnamed officials made new charges against Iran to the Financial Times.
Evidence that Iranian territory is being used as a base by al-Qaeda to help in terrorist operations in Iraq and elsewhere is growing, say western officials.
It is not clear how much the al-Qaeda operation, described by one official as a money and communications hub, is being tolerated or encouraged by the Iranian government, they said.
The groupâ€™s operatives, who link the al-Qaeda leadership in Pakistan with their disciples in Iraq, the Levant and North Africa, move with relative freedom in the country, they said.
The officials said the creation of some kind of al-Qaeda hub in Iran appears to be separate from the group of seven senior al-Qaeda figures, including Saad bin Laden, son of the groupâ€™s figurehead, that Iran is said to have detained since 2002.