Tin Oo: under house arrest since 2004
Burma has freed the vice-chairman of Aung San Suu Kyi's opposition National League for Democracy (NLD).
Tin Oo, 82, has been in prison or under house arrest for more than a decade.
The release comes as Burma's ruling military junta prepares to hold national elections in 2010, though no date has yet been set.
Rumours inside Burma say Ms Suu Kyi could also be freed, probably after the elections, and once her period of house arrest expires in November.
Speaking after officials entered his house and announced his release, Tin Oo said he would continue to work for democracy.
He said he was "very hopeful" Ms Suu Kyi would soon be released, AP reported.
Tomas Ojea Quintana, the UN's special envoy to Myanmar, is due in the country on Monday to assess its progress on human rights issues.
Analysts say Tin Oo could have a key role in deciding whether or not the NLD participates in the forthcoming elections.
Tin Oo, who spent three years in prison after helping to found the NLD in 1988, has been either in prison or under house arrest since he was detained along with Ms Suu Kyi in 2003.
The former defence minister, a highly decorated general, was forced into retirement in 1976. He was later sentenced to hard labour for treason.
In January, Burma's home minister reportedly said Ms Suu Kyi would be freed when her current period of house arrest expires.