A teenager who said he was part of a team of assassins sent to kill former Prime Minister Benazir Bhutto was arrested near the Afghan border, Pakistani officials said on Saturday.

The teen also confessed to taking part in a plot to attack Shiites during the Ashoura festival, even as police in Pakistan's far south said they had foiled suicide attacks planned for the Shiite Muslim festival.

In Karachi, police chief Azhar Farouqi said officers detained five men who were in the possession of explosives, detonators and a small quantity of cyanide intended for attacks on this week's Ashoura processions.

''With these arrests we have foiled major attacks,'' Farouqi said.

The intelligence official said the 15-year-old told investigators that the five-person squad was dispatched to Rawalpindi, where Bhutto was killed, by Baitullah Mehsud, a militant leader with strong ties to al-Qaeda and an alliance with the Taliban in nearby Afghanistan, on Afghanistan's northwest border.

The senior official from Pakistan's North West Frontier Province, who spoke on condition of anonymity, said the teen was arrested on Thursday and was involved in a plot to attack Shiites during an Ashoura festival on Sunday.

A senior district police officer in Dera Ismail Khan, a town 168 miles southwest of Islamabad, confirmed the teen's arrest there and said the suspect made ''a sensational disclosure.'' The officer also asked not to be named because of the sensitivity of the matter.

In Islamabad, Interior Ministry spokesman Jawed Iqbal Cheema said he had no information about any arrests in the border area, or about any new developments in the Bhutto case.

Maulvi Mohammed Umar, a purported spokesman for Mehsud, denied his group had links with the teen, and said he had not been dispatched by Mehsud to kill Bhutto.

''It is just a government propaganda,'' he said. ''We have already clarified that we are not involved in the attack on Benazir Bhutto.''

Bhutto, a former prime minister, died on Dec. 27 when one member of the squad, whom the teen allegedly identified as Bilal, fired at her and detonated an explosive vest as Bhutto was leaving a campaign rally in Rawalpindi, which is adjacent to Islamabad. The blast killed at least 20 other people and wounded scores more.