ISLAMABAD, Pakistan (CNN) -- In what is seen as a blow to the Pakistani Taliban, two top figures from the militant group have been seized by security forces, Pakistani officials said.
The two were identified as Commander Saif Ullah, described by police as the right-hand man of Pakistani Taliban leader Baitullah Mehsud, and Maulvi Umar, the well-known spokesman for the group.
Both were arrested on Monday, the officials said.
Ullah was seized with his brother, Zahid, at a house outside Islamabad, police said. UIlah had been injured in either a drone attack or shelling near the Afghan border and was seeking medical treatment, they said.
He was in charge of terrorist activities in southern Punjab province and worked to recruit suicide bombers and facilitate suicide attacks, one of the officials said.
Ullah is also believed to have had a role in a bombing at Islamabad's Marriott hotel in 2007 and is being questioned about that attack, which killed the suicide bomber and one other person.
Umar was arrested in Pakistan's Mohmand Agency, one of seven semiautonomous tribal agencies along the 1,500-mile porous border that Pakistan shares with Afghanistan, intelligence officials said.
Members of a local militia or "lashkar" detained Umar and handed him over to security forces, a senior intelligence official said.
Hundreds of Pakistani villagers have formed anti-Taliban militias in the wake of the Pakistani military offensive and subsequent Taliban attacks on civilian targets.
Umar was recently in the media spotlight contradicting U.S. officials' contention that Mehsud had been killed in a drone strike.
U.S. and Pakistani government officials have said they are confident that Mehsud was killed in a suspected U.S. drone strike on his father-in-law's house in the South Waziristan tribal region earlier this month.
The Pakistani Taliban have not confirmed Mehsud's death because of an ongoing power struggle over his successor, the top U.S. envoy to the region said Monday.
"The reason it's clear he's dead is that if he weren't dead he'd be giving TV and radio interviews to prove he's not dead," Richard Holbrooke told CNN.
During his interrogation, Umar told authorities that Mehsud was killed in the drone strike, said Mian Iftikhar Hussain, the information minister in the North West Frontier Province.
Last week, Umar told CNN that Mehsud is alive, but ill, and would speak to reporters when he feels better.
Mehsud rarely gave news conferences or appeared before the media.
Other media reports have quoted another spokesman for the group as saying Mehsud is dead and a mourning period is under way.
DNA tests were reportedly being conducted to back up those claims, but U.S. officials have expressed doubt that enough genetic material would be left behind considering the enormity of the strike.
Holbrooke said Mehsud's assumed death has sparked "a succession crisis" among the Pakistani Taliban.
"The chaos benefits us but it doesn't mean that this thing is over," he said.
Mehsud's likely death and this week's arrests are a sign of "the ratcheted-up pressure" that has been placed on the Mehsud network this year, CNN terrorism analyst Peter Bergen said.
"The U.S. has mounted some 20 drone attacks this year in the Pakistani tribal agency of southern Waziristan where the (Baitullah Mehsud) network is based," Bergen said. "That has interfered with the Pakistani Taliban's ability to plan attacks and train others as many of their leaders are now focusing mostly on survival."
CNN's Samson Desta and Nasir Habib contributed to this report.