Police levelled their first formal charge against Myanmar’s ousted leader Aung San Suu Kyi, members of her party said on Wednesday, giving military authorities who staged a coup a legal reason to detain her for at least through the middle of the month.

The charge — that Suu Kyi was in possession of illegally imported walkie talkies — came to light two days after she was placed under house arrest and appeared to be an effort to lend a legal veneer to her detention, though the generals have previously kept her and others locked up for years.

The military announced on Monday that it would take power for one year — accusing Suu Kyi’s government of not investigating allegations of voter fraud in recent elections. Suu Kyi’s party swept that vote, and the military-backed party did poorly.

National League for Democracy spokesman Kyi Toe confirmed the charge against Suu Kyi that carries a maximum sentence of three years in prison. He also said the country’s ousted president, Win Myint, was charged with violating the natural disaster management law. A leaked charge sheet dated Feb 1 indicates they can be held until Feb 15.

“It was clear that the military were going to look for some legal cases against the leaders of the National League for Democracy and especially Aung San Suu Kyi to actually legitimise what they’ve tried to do,” said Larry Jagan, an independent analyst of Myanmar affairs. “And that is really a power grab.”

Police and court officials in the capital Naypyitaw could not immediately be contacted.

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At the same time that authorities were working to keep Suu Kyi in detention, hundreds of lawmakers who had been forced to stay at government housing after the coup were told on Wednesday to leave the capital city within 24 hours and go home, said a member of parliament from Suu Kyi’s party who is among the group. He spoke on condition of anonymity because he feared drawing the attention of the military.

The coup was a dramatic backslide for Myanmar, which had been making progress toward democracy, and highlighted the extent to which the generals have ultimately maintained control in the Southeast Asian country.

In response to the coup, Suu Kyi’s party has called for nonviolent resistance, and scores of people in Yangon, Myanmar’s largest city, honked car horns and banged on pots and pans on Tuesday night in a protest. Supporters of the military have also staged demonstrations.

Medical workers have also declared they won’t work for the new military government in protest of the coup at a time when the country is battling a steady rise in Covid-19 cases with a dangerously inadequate health system. Photos were shared on social media showing health workers with red ribbons pinned to their clothes or holding printed photos of red ribbons.

There were also protests in neighbouring Thailand, where Khin Maung Soo, a Myanmar national, said on Wednesday that he was demonstrating to “show the world that we are not happy with what happened”.

He added: “We want the world to know, and we want the whole world to help us too.”

The takeover marked a shocking fall from power for Suu Kyi, a Nobel Peace Prize laureate who had lived under house arrest for years as she tried to push her country toward democracy and then became its de facto leader after her party won elections in 2015.

Suu Kyi had been a fierce critic of the army during her years in detention. But after her shift from democracy icon to politician, she worked with the generals and even defended their crackdown on Rohingya Muslims, damaging her international reputation.

Timeline: Aung San Suu Kyi, Myanmar's most famous political figure, detained again

The international community, which had enthusiastically supported Myanmar’s nascent democracy, now faces a test. The United States has threatened sanctions and has labelled the takeover a coup. The UN Security Council held an emergency meeting on Tuesday but took no action.

The foreign ministers of the Group of 7 leading industrial nations on Wednesday issued a statement calling for Suu Kyi and others to be released and for power to be restored to the democratically elected government.

While in power, Myanmar’s new leader said the military government plans to investigate alleged fraud in last year’s elections. Senior Gen Min Aung Hlaing announced the moves on Tuesday at the first meeting of his new government in the capital, the state-run Global New Light of Myanmar newspaper said.

While the military has cited the government’s failure to properly investigate allegations of electoral irregularities as one of the reasons for the coup, the state Union Election Commission has said there were no significant problems with the vote.

Analysts have said the landslide victory of Suu Kyi’s party may have caught the military by surprise — and made the generals concerned that it had too much power, even though the constitution had been carefully written to ensure the military maintained significant control, including with an allocation of 25 per cent of the seats in Parliament.

Min Aung Hlaing also said that Covid-19 containment measures taken by Suu Kyi’s government would be continued.

Myanmar has confirmed more than 140,600 cases including some 3,100 deaths. Its health care infrastructure is one of the weakest in Asia, according to UN surveys.

A statement issued on Wednesday in the name of the executive members of Suu Kyi’s party said that authorities began raiding the party’s offices in Mandalay and other states and regions on Tuesday and seized documents and laptop computers.

The statement on the Facebook page of party spokesman Kyi Toe said locks were broken at several offices. It denounced the raids as illegal and demanded that they stop.