Myanmar's government agency in charge of air travel says it has stopped all passenger flights in the country.
The US Embassy in Myanmar said on its Facebook page that the road to the international airport in Yangon, the country's s biggest city, had been closed Monday.
On Twitter it said that “reports indicate that all airports in Myanmar are closed.”
The US Embassy also issued a “security alert” saying it was aware of the detention of Myanmar's leader Aung San Suu Kyi as well as the shutdown of some Internet service, including in Yangon.
“There is potential for civil and political unrest in Burma, and we will continue to monitor the situation,” it said, using Myanmar's former name.
The US State Department earlier issued a statement say it was “alarmed” by Monday's military takeover.
China said it was still gathering information about Monday's developments in Myanmar.
China is one of Myanmar's most important economic partners and has invested billions of dollars in mines, infrastructure and gas pipelines in the Southeast Asian nation.
Foreign Ministry spokesman Wang Wenbin said at a daily news briefing: "We have noted what happened in Myanmar, and we are learning the further situation now,”
He added: “China is a friendly neighbour of Myanmar. We hope that all parties in Myanmar will properly handle their differences under the constitutional and legal framework and maintain political and social stability.”
While China's ruling Communist Party tends to favour fellow authoritarian regimes, it has had a fractious history with Myanmar's military, sometimes related to its campaigns against ethnic Chinese minority groups and the drug trade along their long, mountainous border.
Myanmar'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.
The announcement on military-controlled Myawaddy TV came after an earlier declaration that because national stability was in jeopardy, all government functions would be transferred to military chief Senior Gen. Min Aung Hlaing under a provision in the 2008 constitution that was issued under military rule.
The announcement said once the election is held, the military would hand power to the winner.
Suu Kyi's National League for Democracy party won a landslide victory in last November's general election, humiliating the military-backed opposition Union Solidarity and Development Party.
The military said it acted because Suu Kyi's government failed to address its allegations of widespread voter fraud and other election-related issues.
UN Secretary-General Antonio Guterres has strongly condemned the detention of Myanmar's civilian leaders as the military announced it was taking control of the country for one year.
He expressed “grave concern” about the declaration that all legislative, executive and judicial powers have been transferred to the military.
“These developments represent a serious blow to democratic reforms in Myanmar,” said a statement from the UN chief's spokesperson, Stéphane Dujarric.
Guterres said the elections last November provided a strong mandate for Suu Kyi's National League for Democracy to govern.
The announcement that the military was taking control came on the first day Myanmar's Parliament was to convene following the November elections.
The military has argued those elections were tainted by fraud, but the elections commission last week rejected those claims as lacking evidence.
Human rights groups are calling for the immediate release of Aung San Suu Kyi and other civilian leaders in Myanmar.
A military takeover in the country was announced Monday morning on the day Myanmar's Parliament was to convene with new members sworn in following November elections.
The military has claimed the election was tainted by fraud but an election board rejected those claims as lacking evidence.
Human Rights Watch expressed concern about the safety of the figures being detained.
“The military's actions show utter disdain for the democratic elections held in November and the right of Myanmar's people to choose their own government,” said Phil Robertson, HRW's deputy Asia director.
Amnesty International noted that violence and extrajudicial killings had marked past coups and urged Myanmar's armed forces to exercise restraint.
“The concurrent arrests of prominent political activists and human rights defenders sends a chilling message that the military authorities will not tolerate any dissent,” Amnesty International said.
Leaders in the Asia-Pacific region are expressing concern about the military's actions in Myanmar and detentions of top civilian leaders.
Myanmar military television said Monday morning the military was taking control of the country for one year and Suu Kyi and others had been detained.
The actions came on the day Myanmar's Parliament was to convene with new members sworn in following November elections.
Australian Prime Minister Scott Morrison reiterated his country's opposition to any attempt to alter the election results and urged all parties to adhere to democratic norms.
Japan's Chief Cabinet Secretary Katsunobu Kato said the government had issued a safety advisory to Japanese citizens to be careful in the event of possible clashes.
“Japan believes it is important to resolve the problem peacefully through dialogue between the related parties based on democratic process,” Kato said.