Burma is grappling with a military coup on the day that the new parliamentary session was set to begin, with many in the international community denouncing the power grab as a threat to the strained progress made over the past 10 years.

The Burmese military arrested democratically elected State Counsellor Aung San Suu Kyi and other officials, announcing on the military-owned Myawaddy TV that the military would assume control for one year.

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.

Buddhist religious and military flags are waved by supporters including Buddhist monks onboard a vehicle Monday, Feb. 1, 2021, in Yangon, Burma. Burma's military has announced it will hold a new election at the end of a one-year state of emergency it declared Monday when it seized control of the country and reportedly detained leader Aung San Suu Kyi. (AP Photo/Thein Zaw)

Supporters of the military and the leading opposition party, Union Solidarity and Development Party, held small rallies on Monday to celebrate the ousting of Suu Kyi's National League for Democracy party.

Trucks carried people and loudspeakers through Yangon, the country’s biggest city, with many displaying national or Buddhist flags.

BURMA'S LEADER AUNG SAN SUU KYI AND OTHER OFFICIALS ARRESTED, PARTY SPOKESMAN SAYS

The international community has largely condemned the swift power grab, with U.N. Secretary-General Antonio Guterres expressing "grave concern" about the declaration that all powers have been transferred to the military.

"These developments represent a serious blow to democratic reforms in Myanmar," said a statement from the U.N. chief's spokesperson, Stéphane Dujarric.

FILE - In this Nov. 8, 2020, file photo, Burma military Commander-in-Chief Senior Gen. Min Aung Hlaing leaves a polling station after voting in Naypyitaw, Burma. (AP Photo/Aung Shine Oo, File)

Jen Psaki, the White House press secretary, said the U.S. is "alarmed" by reports from Burma. President Biden has been briefed on the unfolding situation by national security adviser Jake Sullivan.

"We continue to affirm our strong support for Burma’s democratic institutions and, in coordination with our regional partners, urge the military and all other parties to adhere to democratic norms and the rule of law, and to release those detained today," she said. Psaki said the U.S. will "take action against those responsible" if the steps "are not reversed."

WHY IS THE MILITARY TAKING CONTROL IN BURMA?

Turkey’s foreign ministry said that in a statement that the country "is opposed to all kinds of coups and military intervention." It also expressed concern that the coup could exacerbate the situation of minority Rohingya Muslims.

British Prime Minister Boris Johnson tweeted: "I condemn the coup and unlawful imprisonment of civilians, including Aung San Suu Kyi, in Myanmar. The vote of the people must be respected and civilian leaders released."

China took a more muted response, saying that it hoped "all parties in Myanmar will properly handle their differences under the constitutional and legal framework and maintain political and social stability."

In this May 6, 2016, file photo, Aung San Suu Kyi, left, Burma's foreign minister, walks with senior General Min Aung Hlaing, right, Burma military's commander-in-chief, in Naypyitaw, Burma. (AP Photo/Aung Shine Oo, File)

The coup follows days of escalating tensions during which many observers accused the military of planning to usurp powers. The military had cried foul over voter fraud after losing last year’s election.

Gen. Min Aung Hlaing reportedly told senior officers on Wednesday that the country’s constitution could be revoked if the laws were not being properly enforced – a constitution the military crafted over a decade ago.

The constitution also provided the means by which the military was able to usurp power: Article 417 allows the military to assume power in times of emergency.

The military had demanded a delay to the Nov. 8 election, citing the coronavirus pandemic as a safety concern.

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The ruling National League for Democracy party won 396 of the available 476 in November’s election, with the military-backed USDP securing only 33 seats.

This is a developing story. 

The Associated Press contributed to this report.