Opponents of military rule in Myanmar marked the one-year anniversary of the army's seizure of power with a nationwide strike Tuesday to show their strength and solidarity amid concerns about what has become an increasingly violent contention for power.

The "silent strike" sought to empty the streets of Myanmar's cities and towns by having people stay home and businesses shut their doors from 10 a.m. to 4 p.m.

In Yangon, the country's largest city, and elsewhere, photos on social media showed normally busy streets almost empty.

The anniversary has also attracted international attention, especially from Western nations critical of the military takeover, such as the United States.

U.S. President Joe Biden in a statement called for the military to reverse its actions, free the country's ousted civilian leader Aung San Suu Kyi and other detainees and engage in meaningful dialogue to return Myanmar to a path of democracy.

The military's takeover on Feb. 1, 2021, ousted the elected government of Suu Kyi, whose National League for Democracy (NLD) party was about to begin a second five-year term in office after winning a landslide victory in the previous year's November election. The military said it acted because there was widespread voter fraud in the polls – an allegation that independent election observers have said they've seen no serious evidence of.

Widespread nonviolent demonstrations followed the army's takeover initially, but armed resistance arose after protests were put down with lethal force. About 1,500 civilians have been killed, but the government has been unable to suppress the insurgency, which some United Nations experts now characterize as a civil war.

The U.S. on Monday imposed new sanctions on Myanmar officials, adding to those already applied to top military officers. They freeze any assets that those targeted may have in U.S. jurisdictions and bar Americans from doing business with them. Britain and Canada announced similar measures.

Washington sanctioned Attorney General Thida Oo, Supreme Court Chief Justice Tun Tun Oo and Anti-Corruption Commission chairperson Tin Oo, all of whom it said were closely involved in the "politically motivated" prosecution of Suu Kyi.

"We are coordinating these actions with the United Kingdom and Canada... to further promote accountability for the coup and the violence perpetrated by the regime," U.S. Secretary of State Antony Blinken said. Citing "unspeakable violence against civilians," the undermining of regional stability and "rampant" corruption, Biden said he was working with allies to "hold accountable" those responsible.

A statement from the office of U.N. Secretary-General Antonio Guterres highlighted "an intensification in violence, a deepening of the human rights and humanitarian crises and a rapid rise of poverty in Myanmar," which it said required an urgent response.

People in Myanmar rushed before the start of Tuesday's strike to buy essentials, and in Yangon appeared to have done their shopping on Monday. The junta had ordered shops to stay open Tuesday, following activist calls for a "silent strike" on the anniversary.

But the streets of commercial hub Yangon began emptying at 10 a.m., Agence France-Presse (AFP) correspondents said, a scene that repeated in the city of Mandalay and southern Tanintharyi region.

Pro-democracy flash mob marches were held in several places before the start of the strike in the early morning hours, when clashes with police and soldiers are less likely.

On Tuesday, an explosion took placed during a procession of military supporters in the eastern border town of Tachileik, two witnesses told Reuters. The blast killed two people, said one of the witnesses, and wounded more than 30 others.

Local media reported ongoing violence on Monday, with at least six bombings believed to have been carried out by resistance forces in Yangon, and another at a police station in Myitkyina in northern Kachin state. The opposition carries out daily guerrilla actions, while the military engages in larger-scale assaults in rural areas, including airstrikes, which are blamed for many civilian casualties.

Despite tight security in cities including Yangon, Mandalay and Sagaing, young protesters including Buddhist monks held a passionate protest at dawn, carrying banners and chanting anti-military slogans.

Many also held up three fingers, the resistance salute adopted from the film "Hunger Games" that has also been used by pro-democracy demonstrators in neighboring Thailand.

Shopkeepers have been threatened with arrest by the authorities; consequently, some were open for business Tuesday but appeared to have few if any customers.

Since last week, the government had issued official warnings in state-run media that anyone taking part in the strike could be prosecuted, including under the country's counterterrorism law with a maximum penalty of life imprisonment and the possible confiscation of their property.

Dozens of business owners who had announced they planned to be closed were arrested, according to reports in the state-run newspaper Myanma Alinn Daily.

The detainees, from areas around the country, included shopkeepers, restaurant owners, medical workers, a monk, a makeup artist, a mobile phone repair shop owner and an astrologer.

The military-installed government initiated other measures to try to undercut the strike. In Yangon and Mandalay, city administrators scheduled special events, including a cycling contest, to try to draw crowds. City workers in Yangon were told to attend during strike hours, according to leaked documents posted on social media.

Several pro-military demonstrations, widely believed to have been organized by the authorities, were also held.

Leaders of the opposing sides also broadcast speeches marking the anniversary.

Duwa Lashi La, acting president of the opposition's National Unity Government (NUG), said the group is understood by the people as the guiding force of the revolution, and it promises to do its utmost to make the revolution a success. The NUG, established by elected lawmakers, considers itself the country's legitimate administrative body and has won the loyalty of many citizens. The military has branded it a "terrorist" organization.

Senior Gen. Min Aung Hlaing, leader of the military-installed government, reviewed its performance since taking power in an hourlong speech. He pledged a "genuine and disciplined multiparty democratic system," calling for cooperation "so as to achieve a better future for the country and people."

The new U.N. special envoy for Myanmar said Monday that violence and brutality have intensified since the military took power, sparking a resistance movement in the country, and all sides have hardened their positions on "using violence as a solution."

Noeleen Heyzer told a virtual news conference at U.N. headquarters in New York that Myanmar’s situation is increasingly unstable and military operations, including artillery attacks and airstrikes, have raised concerns about the protection of civilians.

She said around 1,500 civilians have been killed in the past year and the number of internally displaced people rose from more than 320,000 at the end of 2021 to over 400,000 now, according to The Associated Press (AP). "This is in addition to the 340,000 people already displaced before Feb. 1, 2021," when the military seized power.

Heyzer, who took up the post six weeks ago, said almost half of Myanmar’s population now live in poverty and more than 14.4 million people are estimated to need humanitarian assistance and protection.

She acknowledged proposals brought by the Association of Southeast Asian Nations' (ASEAN) new leader, Cambodian President Hun Sen, after he visited Myanmar in December.

Heyzer called one proposal "interesting" but "not sufficient" – to hold a humanitarian meeting to help deliver assistance that was part of the five-point consensus to which ASEAN leaders agreed to help restore peace and security to Myanmar. She said she wasn’t satisfied with the mechanism to ensure aid was delivered without discrimination.

Heyzer said she agreed to help support facilitating a humanitarian meeting and has asked for "a humanitarian pause" and "a possible humanitarian corridor in the areas that are not under the control of the military" to ensure people there can receive aid.

She said ASEAN foreign ministers and some leaders are pressuring Myanmar to implement the entire five-point consensus reached at the bloc's meeting last April that included Min Aung Hlaing. Other points include an immediate halt to violence, starting a dialogue among all parties, and the appointment of an ASEAN special envoy. But Heyzer said ASEAN members remain divided on the pressure tactics and on Myanmar’s representation in the 10-nation group.

Heyzer stressed that progress is possible if all parties work together.

"We have a window of opportunity to build upon a unique unity across religious, ethnic and communal lines," Heyzer said. "The road ahead will be long and difficult, but the time to act is now, and time is running out," she added.