The sources told AFP that Iran could strike the biggest blow to al-Qaida network if it handed over top members detained in the Islamic republic to their countries.
“There is firm reason to believe that Iran is holding some senior al-Qaida,” a source said.
“But the negotiations to hand them over are very delicate, so for the moment there has been no official word on who they are,” the source added.
The sources said they had strong reason to believe that three top al-Qaida officials were held in Iranian custody.
One is Egyptian-born Saif al-Adl, who is believed to have replaced military operations chief Muhammad Atef.
Atef is thought to have been killed in Afghanistan.
The second is Saad bin Laden, one of the sons of al-Qaida chief, Usama bin Ladin.
Saudi Arabia has stripped him of his Saudi citizenship.
Saad is thought to have become a senior figure in the network, which Washington accuses of being behind attacks against Americans worldwide.
The third is Kuwaiti-born Sulaiman Abu Ghaith, who is al-Qaida spokesman. Kuwait has stripped him of his citizenship.
The Dubai-based news channel, al-Arabia, quoted Western diplomatic sources as saying that Egyptian-born Ayman al-Zawahiri could also be one of the detainees held in Iran.
Al-Zawahiri is believed to be al-Qaida’s number two.
Identities kept secret
Diplomats said they were unsure if Abu Mussab al-Zarqawi, who Washington says was the mediator between the former Iraqi regime and al-Qaida, had also been detained in Iran.
Iran, however, has refused so far to release the identities of its detainees.
Government spokesman Abd Allah Ramezanzadeh told AFP on Saturday that the identification process of many of the detainees was continuing.
But he added that it was unlikely for Iranian authorities to release their names.
“We have not been able to identify all al-Qaida members, and even if we did there is no reason for us to give their names to the press,” Ramezanzadeh said.
“This is a security issue and this is how security apparatuses work," he added.
Diplomats said negotiations to extradite the detainees were facing obstacles.
Iran has only low-level diplomatic relations with Egypt, which is negatively affecting the extradition talks.