YANGON (REUTERS) - Myanmar's new lawmakers vowed to take their seats in Parliament for the first time and said they were undaunted by threats from the army and fears of a coup after the military alleged last year's election was fraudulent.

Myanmar's powerful military last week threatened to "take action" over alleged fraud in a November election won by the party of Ms Aung San Suu Kyi, just days before the Parliament was set to convene.

In a statement on Saturday (Jan 30), the army appeared to backtrack, saying it would protect and abide by the Constitution and act according to law, but pro-military demonstrations continued in major cities.

About 300 people marched through the commercial capital of Yangon on Sunday waving banners and chanting in support of the military and against foreign intervention in the country's internal affairs.

A military spokesman did not answer phone calls seeking comment.

The National League for Democracy (NLD) led by Ms Suu Kyi, a former political prisoner and figurehead of Myanmar's long struggle against dictatorship, won 83 per cent of available seats in the Nov 8 election seen as a referendum on her fledgling democratic government.

The military has disputed the result and legal complaints against the country's president and chair of the electoral body are pending at the Supreme Court.

The election commission has rejected the allegations, saying there were no errors big enough to affect the credibility of the vote.

Myanmar's lower house is set to convene on Monday but state media announced over the weekend the first session of the upper house had been rescheduled to Tuesday.

Under the country's Constitution, a quarter of seats are reserved for lawmakers from the military, which has declined to comment on whether they will attend.

Mr Monywa Aung Shin, a spokesman for the NLD, said representatives from all parties including those from the military were receiving vaccinations against Covid-19 in order to attend Parliament on Monday.

"I believe that everyone will attend the Parliament tomorrow," he told Reuters by phone.

Many lawmakers from the ruling party spent years in jail under the former military government, which ruled for half a century until reforms began in 2011.

Several told Reuters they were not frightened by the signs of increased tensions, including armed police patrolling at the housing where they have been quarantining ahead of the Parliament session.

"I will go to Parliament on Monday, as we are members of Parliament elected by the people," said NLD lawmaker Phyu Phyu Thin, a former political prisoner.

"This is not new for us," she said.

Mr Nai San Tin, a representative from the Mon Unity Party, said he was prepared to face any situation.

"We knew we would experience this kind of situation sooner or later," he told Reuters by phone.

"Especially being a politician in Myanmar, we cannot avoid this."