A leader of Myanmar's recent mass protests was arrested Wednesday, and a member of the opposition party has died during interrogation by security forces, an exile group said.

The Thailand-based Assistance Association for Political Prisoners also said security officers had been threatening dissidents' relatives and neighbors in order to get information on the whereabouts of those involved in last month's pro-democracy protests that were brutally suppressed by the military regime.

"The security forces have become more severe in raiding houses of, and searching for, anyone whom they suspect to have been involved in the protests," it said.

The Myanmar exile group, made up of former political prisoners, said authorities had recently informed the family of Win Shwe, 42, that he had died during interrogation in the central Myanmar region of Sagaing. He and five colleagues were arrested on Sept. 26.

The body of Win Shwe, a member of pro-democracy leader Aung San Suu Kyi's National League for Democracy, was cremated at the detention center, the group said. The report could not be independently verified, although in the past the group has provided detailed, accurate information on political prisoners in the country.

White House foreign affairs spokesman Gordon Johndroe condemned Win Shwe's death and warned that the United States would impose new sanctions against Myanmar, also known as Burma, if it continued its crackdown on dissidents.

"The United States strongly condemns the atrocities committed by the junta and calls for a full investigation into the death of Win Shwe during his detention in Burma," Johndroe said. "The junta must stop the brutal treatment of its people and peacefully transition to democracy or face new sanctions from the United States."

First lady Laura Bush, who has been an outspoken advocate for human rights in Myanamar, also warned the U.S. was considering sanctions unless the government loosens its grip on the populace.

"The crackdown has been brutal," she said in an interview with USA Today published Tuesday.

The National League for Democracy won a landslide election victory in 1989, but the parliament was never allowed to convene by the military junta.

The Assistance Association for Political Prisoners said that at least seven people have been arrested in the past two days in Yangon, even as the junta and the NLD appeared to be taking cautious steps toward talks.

Hla Myo Naung, a leader of the '88 Generation Students, was arrested in Yangon while seeking treatment for a serious eye problem at a clinic, the exile group said. Hla Myo Naung, 39, had been on the regime's "wanted list" but had evaded arrest for two months. A young woman who belongs to the '88 Generation and had been with him was also arrested.

The '88 Generation organized marches in August over a fuel price increases that quickly ballooned into mass demonstrations calling for democracy when widely respected Buddhist monks began taking the lead.

Troops crushed the protests by shooting at demonstrators Sept. 26-27. The regime said 10 people were killed, but dissident groups put the toll at up to 200 and say thousands of students, Buddhist monks and others were arrested.

The brutal crackdown ignited international outrage.

In the face of such pressure, the junta's top general offered last week to meet with Suu Kyi, a Nobel Peace laureate who has been under house arrest for 12 of the past 18 years without trial. He said she must first renounce her calls for international sanctions against the regime, which has been widely condemned for crushing last month's protests.

The junta also appointed a relatively flexible Cabinet-level official to coordinate contacts with Suu Kyi, 62, whose league said it was prepared to make "adjustments" for the sake of dialogue.

The appointment of Aung Kyi, a retired major general, appeared to be a gesture toward the United Nations. The world body's special envoy, Ibrahim Gambari, suggested creating the Cabinet-level job during his visit to Myanmar last week, state media said.

Small groups of riot police Wednesday patrolled key road junctions and sites where the most intense protests had erupted, including the Shwedagon Pagoda and a junction near the downtown Sule Pagoda. But soldiers were not visible on the streets, and Yangon seemed generally normal.

The state-owned New Light of Myanmar newspaper said 60,000 pro-government demonstrators had gathered Tuesday in Paan in eastern Myanmar to support the junta's own "roadmap to democracy" while denouncing the United States and foreign radio stations.