Myanmar's military seized power on Monday in a coup against the democratically elected government of Aung San Suu Kyi.
Other senior figures from the country's ruling party were detained in what the party's spokesman called an early morning raid.
On Military-owned TV, the Myanmar army declared a state of emergency and said it carried out detentions in response to election fraud.
Dozens of soldiers were around the city hall in major city Yangon shortly after the reported arrests.
Phone lines to the nation's capital Naypyidaw were not reachable immediately after.
Parliament had been set to start there on Monday after a November election.
State-run television MRTV showed no signal and said in a Facebook post it had stopped its broadcast due to technical issues.
A ruling party lawmaker, who requested anonymity for fear of retaliation, said Han Thar Myint, a member of the party's central executive committee, was among those detained.
A military spokesman did not answer phone calls seeking comment.
The arrests come after last November's election, which gave Suu Kyi's party, the National League for Democracy, a landslide victory.
The military, which controls key positions in parliament and Suu Kyi's administration, has called the election fraudulent, but they promised over the weekend to protect and uphold the constitution after suggesting earlier that week they would abolish it, raising fears of a coup.
Meanwhile, Myanmar's election commission has rejected the military's allegations of vote fraud.
Suu Kyi came to power in 2015 in a landslide election... following decades of military house arrest in a struggle for democracy.
She had won the Nobel Peace prize for her effort, but her international standing was damaged after hundreds of thousands of the Rohingya people fled military violence in 2017.
At home, she still remains widely popular.