The roundups, which could still be under way, occurred as a bomb blast at a mosque in Pakistan's northwestern tribal belt killed 29 people including some militants Thursday and US special envoy Richard Holbrooke met with Pakistani leaders here.

The latest arrests took place late Wednesday and early Thursday when nine militants linked to Al-Qaeda were nabbed near Karachi, where the Taleban's deputy chief Mullah Abdul Ghani Baradar was picked up several days ago.

Others picked up in the recent sweeps included the Taleban's 'shadow' governors in two provinces in northern Afghanistan, according to the official governor of the Afghan province of Kunduz, Mohammad Omar, and two Pakistani intelligence officers.

Communications intercepted by US authorities played a key role in tracking and arresting the suspects, who were in Karachi buying bomb-making equipment, the officials said. They were taken to Islamabad for questioning.

Details of the arrests were unclear, including how they were linked to the capture of Mullah Baradar, who effectively ran the Taleban on a day-to-day basis on behalf of the reclusive leader Mullah Mohammad Omar.

But a Pakistani intelligence official said Mullah Baradar has provided “useful” information that has led to the arrests of other suspected militants. The official said Mullah Baradar was traveling in a car on the outskirts of Karachi when he was nabbed along with three of his guards. He said Mullah Baradar was picked up with help from the CIA.

Pakistan security agencies conducted three different raids on Wednesday night in Karachi and arrested nine more suspects including three foreigners. Among those arrested in the three Karachi area raids were Ameer Muawiya, an associate of Al-Qaeda leader Osama Bin Laden who was in charge of foreign Al-Qaeda militants operating in Pakistan's tribal regions; Akhunzada Popalzai, also known as Mohammad Younis, a one-time Taleban shadow governor in Zabul province; Hamza, who served as a former Afghan Army commander in Helmand province during the Taleban rule; Abu Riyan Al-Zarqawi, also known as Abu Musa; and his local facilitator, Mufti Kifayatullah.

Al-Zarqawi was involved in dealing with Chechen and Tajik militants operating in Pakistan's tribal belt. The two Taleban shadow governors — Mullah Abdul Salam of Kunduz province and Mullah Mohammad in Baghlan province — were arrested about 10 to 12 days ago in Pakistan, according to Afghan and Pakistani officials.

Both were key figures in the Taleban's expansion to northern Afghanistan, where their forces threatened NATO supply lines coming south from Central Asia and raised alarm that the militants were extending their influence nationwide.

The two Pakistani intelligence officials said Salam was arrested in the Pakistani city of Faisalabad.

Thursday’s bomb explosion tore through a mosque in the Aka Khel area of Khyber, killing at least 29 people and wounding 50, local official Jawed Khan said. Earlier reports had said the blast occurred in the Orakzai area at a cattle market. The two areas border one another, and the market is apparently near the mosque.

Officials were still investigating whether the explosion was caused by a suicide bomber or a planted device.

No group claimed responsibility, but Khan said the dead included fighters from Lashkar-e-Islam, a group in Khyber that has clashed with another outfit known as Ansarul Islam. Both espouse Taleban-style ideologies.

Meanwhile, Holbrooke, on his second visit to Pakistan this year, met Pakistani Prime Minister Yousaf Raza Gilani for talks that included security issues, Gilani's office said. The previous day in Kabul, Holbrooke called the arrest of Baradar "a significant development.”