Myanmar’s opposition party led by detained democracy leader Aung San Suu Kyi on Monday called for the release of activists who were beaten and arrested by a militia group earlier this month.

The 14 activists were detained outside the headquarters of Aung San Suu Kyi’s National League for Democracy (NLD) party on her 63rd birthday on June 19, when they stood on a sidewalk and shouted slogans calling for her freedom.

“The arrest was not in accordance with the law. It was also against the prevalence of law and order,” the National League for Democracy (NLD) party said in a statement.

“The NLD seriously urges the immediate release of all those detainees who were arrested and detained on June 19,” it said.

Myanmar’s police chief confirmed last week that 14 of Aung San Suu Kyi’s supporters had been detained. He originally appeared to confirm the arrests of another group of activists in May, but police officials later clarified that he was referring to the group detained on her birthday.

Aung San Suu Kyi, the world’s only Nobel Peace Prize winner currently in detention, has spent most of the last 18 years confined to her home. Myanmar’s military junta extended her house arrest by another year in May.

She led her party to a landslide victory in 1990 elections, but has never been allowed to govern.

Her party accused the pro-junta Union Solidarity and Development Association (USDA) as well as a militia group called Swan Arr Shin of beating the activists while they were praying for Aung San Suu Kyi’s good health.

“No one prohibited or controlled the violence of the arrest and beating of the NLD members,” the statement said.

“The USDA members and Swan Arr Shin think of themselves as security personnel, placing themselves before the security organisations such as the police,” the statement said.

The party said a letter expressing their concern had already been sent to junta leader Than Shwe.