Two hydropower projects were the target of a series of explosions, while 10 people were killed and at least 170 wounded on April 15, when a water festival in Yangon was bombed in the city's worst attack in five years.
The blasts came as the country readies for the election, which critics say will lack credibility because of laws that effectively bar detained opposition leader Aung San Suu Kyi from taking part.
The poll will be the country's first since 1990 but Aung SanSuu Kyi's National League for Democracy (NLD) party has announced a boycott over the rules, which would have forced it to expel her as leader if it wanted to participate.
Ministers 'quit military'
Thein Sein, the premier, and 22 other ministers retired from their military posts on Monday in a move seen as converting the leadership to civilian form in advance of the vote.
The military has ruled Myanmar since 1962, partly justifying its grip on power with the need to fend off ethnic rebellions that have plagued remote border areas for decades.
Armed minorities in Karen and Shan states continue to fight the government along the country's eastern border, alleging they are subject to neglect and mistreatment.
Foreign governments have urged the regime to take steps to ensure the vote is free, fair and credible.
The last was won by the NLD in a landslide but never recognised by the junta.