Myanmar's leader Aung San Suu Kyi and other senior figures from the ruling party have been detained in an early morning raid, the spokesman for the governing National League for Democracy (NLD) said on Monday.
The move came after days of escalating tension between the civilian government and the powerful military that stirred fears of a coup in the aftermath of an election the army says was fraudulent.
NLD spokesman Myo Nyunt told Reuters by phone that Suu Kyi, President Win Myint and other leaders had been "taken" in the early hours of the morning.
"I want to tell our people not to respond rashly and I want them to act according to the law," he said, adding that he expected to be arrested himself. Reuters was subsequently unable to contact him.
Phone lines to Naypyitaw, the capital, were not reachable in the early hours of Monday. Parliament had been due to start sitting there on Monday after a November election the NLD had won in a landslide.
A military spokesman did not answer phone calls seeking comment.