The United Nations human rights watchdog is “closely following” the arrest and charging of 15 pro-democracy leaders in Hong Kong, reminding the territory’s government of its obligations to international law.

Last week authorities arrested pro-democracy leaders and activists including 81-year-old Martin Lee QC, the founder of Hong Kong’s democratic party and internationally recognised advocate, media tycoon Jimmy Lai, and veteran politician and activist Lee Cheuk Yan.

The arrests were widely criticised, including by the US, UK and Australian governments, and accusations that Beijing was using the pandemic as a cover to crackdown on pro-democracy leaders.

On Friday, the UN’s office of the human rights commissioner said it was “closely following the cases brought against 15 activists”.

“We remind the [Hong Kong] government of its obligations under [the international covenant on civil and political rights] and we hope it will continue to engage with all stakeholders to find solutions for the future benefit of all,” it said.

#HongKong: We are following closely the cases brought against 15 activists. We remind the HKSAR Government of its obligations under ICCPR and we hope it will continue to engage with all stakeholders to find solutions for the future benefit of all. — UN Human Rights (@UNHumanRights) April 23, 2020

In response to the UK and US statements, China’s foreign ministry accused the governments of attempting to “whitewash, condone and exonerate the anti-China troublemakers in Hong Kong”.

The charges against the 15 relate to organising and participating in three protests last year, including one in August which saw 1.7m people attend.

The protests which rocked the city for much of last year were sparked by a proposed bill which would allow for extradition of people from Hong Kong to mainland China. By the time the Hong Kong government agreed to withdraw the bill, the protests had grown into a pro-democracy movement which also called for action on police brutality against protesters during the frequently violent clashes.

This week UN human rights experts wrote to the Chinese government expressing concern at “the harassment, intimidation and arrest” of first aiders and healthcare workers during the protests.

The special rapporteurs, with a working group on arbitrary detention, said they’d received reports that “large numbers of healthcare workers have been arrested and hand-cuffed with zip-cords either in the vicinity of violent confrontations or in the course of performing their legitimate healthcare duties”.

Some were reportedly arrested even after providing identification as healthcare workers and were detained for 24 hours without access to lawyers.

They also received reports of armed police patrolling hospitals in full riot gear, and of undercover police officers who “allegedly impersonated first-aiders to arrest injured protesters”.

This week police said they would not allow annual Labour Day marches to go ahead. The South China Morning Post reported police were also examining whether to allow the June 4 vigil of the Tiananmen Square massacre to go ahead.

Lee Cheuk Yan, secretary of the Confederation of Trade Unions, and who was arrested both last week and in February over the protests, said the May 1 protests would go ahead. Lee said they could ask people to march in groups of four and distanced from others, to comply with social distancing rules.

“It is absurd that police want to ban our rally even if we can make arrangements to satisfy the social-gathering restrictions,” he said.