( Foxnews ) - 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.