Pakistan's powerful Inter-Services Intelligence agency and Islamist militants are the main suspects in the assassination of former premier Benazir Bhutto [Images], British media reported on Friday.

"The foreign and Pakistani Islamist militants saw Bhutto as a Westernised heretic and an American stooge and had repeatedly threatened to kill her.

"But fingers will also be pointed at the ISI which has had close ties to the Islamists since the 1970s and has been used by successive Pakistani leaders to suppress political opposition," The Times of London [Images] reported.

Bhutto narrowly escaped an assassination attempt in October when a suicide bomber struck at a rally in Karachi to welcome her back after eight years in exile.

Bhutto had said after the attack that she had received a letter signed by someone claiming to be a friend of al Qaeda and Osama bin Laden, threatening to slaughter her like a goat.

Earlier in October, two Pakistani militant warlords based in the country's northwestern areas had threatened to kill her. One was Baitullah Mehsud, a top militant commander fighting the Pakistani Army in South Waziristan, who has ties to al Qaeda and the Afghan Taliban.

The other was Haji Omar, the leader of the Pakistani Taliban, who is also from South Waziristan and fought with the Afghan Mujahidin against the Soviets in Afghanistan.

But she also accused Pakistani authorities of not providing her with sufficient security, and hinted that they may have been complicit in the Karachi attack.

Bhutto indicated that she had more to fear from unidentified members of a power structure that she described as allies of the forces of militancy.

Quoting analysts, the report said President Pervez Musharraf [Images] is unlikely to have ordered her assassination, but that elements of the army and intelligence service stood to lose money and power if she became prime minister.

The ISI includes some Islamists who became radicalised while running the American-funded campaign against the Soviets in Afghanistan and were opposed to her on principle.

Saudi Arabia is also thought to have frowned on Bhutto as being too secular and Westernised and to have favoured another former premier Nawaz Sharif.