Sweep follows military questioning of election results with Parliament due to sit this week.
Burmese leader Aung San Suu Kyi and other ruling party figures were arrested in an early morning raid, a spokeswoman for the ruling National League for Democracy said on Monday.
The move comes after days of escalating tension between the civilian government and the mighty military that has sparked fears of a coup following an election the military calls fraudulent.
Spokesman Myo Nyunt told Reuters by telephone that Aung San Suu Kyi, President Win Myint and other leaders were “taken away” in the wee hours of the morning.
“I want to tell our people not to respond recklessly and I want them to act according to the law,” he said, adding that he also expected to be detained.