Islamabad (PTI): Former National Security Adviser Mahmud Ali Durrani, who was sacked after disclosing to media the Pakistani nationality of Mumbai attacker Ajmal Kasab, has said he had the written authorisation from the Prime Minister to speak on the evolving situation in the wake of the 26/11 strikes.

Durrani, a retired Major General who served as Pakistan's envoy to the US and Military Secretary to former President Gen Zia-ul-Haq, also claimed that President Asif Ali Zardari had phoned him and "regretted his dismissal" by Premier Yousuf Raza Gilani last week.

Gilani had said that Durrani -- who was selected by Zardari for the post of NSA last year -- was fired for his "irresponsible behaviour" and for speaking on Kasab's case without taking government into confidence.

However, Durrani told Pakistani newspapers that he was authorised by the Prime Minister in writing to speak on matters of national security and Indo-Pak relations, and it was his understanding that the Kasab issue was within this domain.

Durrani said a reason for his dismissal might be Gilani's feeling that he was being "left out" of the process for making key decisions.

Media reports have suggested that Durrani's sacking was a fallout of differences that have recently emerged between Gilani and Zardari.

An official letter issued on the directive of the Prime Minister last month said only the National Security Adviser, Foreign Minister and Information Minister were authorised to speak on the "evolving situation" in the wake of the Mumbai attacks, according to Durrani.