US and "internal powers" were behind the 1988 plane crash that killed General Zia-ul-Haq, who ruled Pakistan from 1978 till his death, a former Pakistani spymaster has claimed.
Imtiaz Ahmed, a former chief of the Intelligence Bureau, said the US collaborated with "internal powers" in Pakistan to assassinate Zia.
Ahmed, who also served in the ISI, has shaken up political parties with revelations of huge payments allegedly made by the Inter-Services Intelligence to strengthen the opposition to former premier Benazir Bhutto in 1990.
"Former army chief Gen Mirza Aslam Beg also says that Zia's plane crash was not an accident, but sabotage," he told a TV news channel.
Zia came to power after overthrowing the then Prime Minister Zulfikar Ali Bhutto in 1977, the third ruler to impose martial law. He initially ruled as the Chief Martial Law Administrator, but later installed himself as the President of Pakistan in September 1978.
Zia's death in a military plane crash in August 1988 remains shrouded in mystery, which has given rise to several conspiracy theories.
Reports have suggested the plane crashed due to sabotage or mechanical failure.
Reacting to Ahmed's claim, Zia's son Ijaz-ul-Haq demanded that a thorough criminal investigation should be conducted into the plane crash.