WASHINGTON: The Central Intelligence Agency has concluded that the assassins who killed former Prime Minister Benazir Bhutto of Pakistan last month were directed by Baitullah Mehsud, a Pakistani militant leader, and that some of them had ties to Al Qaeda.

The CIA's judgment is the first formal assessment by the U.S. government about who was responsible for the Bhutto assassination, which took place during a political rally in the garrison city of Rawalpindi in Pakistan.

"There are powerful reasons to believe that terror networks around Baitullah Mehsud were responsible," said one U.S. intelligence official, speaking on condition of anonymity because he was not authorized to talk publicly on the matter.

The official said that "different pieces of information" had pointed toward Mehsud's responsibility, but he would not provide details about the information that led to the CIA's conclusion.

General Michael Hayden, the CIA director, discussed the agency's conclusion in an interview published Friday by The Washington Post.

Some friends and supporters of Bhutto questioned the CIA conclusions, especially because the former leader was buried before a full forensic investigation was conducted. The British government has since sent a team from Scotland Yard to participate in the investigation.

"The CIA appears too eager to bail out its liaison services in Pakistan, who are being blamed by most Pakistanis," said Husain Haqqani, a former adviser to Bhutto, now a professor at Boston University. "Given the division inside Pakistan on this issue, it might be better to have an international investigation under the aegis of the UN."

Within days of Bhutto's assassination on Dec. 27, the Pakistani authorities announced that they had intercepted communications between Mehsud and militant supporters in which they said the leader congratulated his followers for the killing.

Mehsud, through a spokesman, has denied responsibility and suggested that the assassins were directed by President Pervez Musharraf of Pakistan, a longtime rival of Bhutto's.

Members of Bhutto's political party, and some family members, have also challenged Pakistani government accounts of the assassination. They have blamed Musharraf for failing to provide Bhutto with adequate protection, and some have hinted that elements of the government might have been behind the killing.

Mehsud's followers have been blamed for many recent suicide attacks against government, military and intelligence targets in Pakistan. Based in the South Waziristan tribal areas, the militant leader is known to run training camps, prepare and dispatch suicide bombers on both sides of the Afghanistan-Pakistan border and have links to the Arab and Central Asian militants who have established a stronghold in the tribal areas.