Navi Pillay, United Nations High Commissioner for Human Rights, is writing to King Hamad bin Isa Al-Khalifa to press her concerns at the harsh sentences laid down on very broad charges, her spokeswoman Ravina Shamdasani said.

“There are serious concerns that the due process rights of the defendants, many of whom are well-known human rights defenders, were not respected, and the trials appear to bear the marks of political persecution,” Shamdasani told a news briefing in Geneva.

Bahrain sentenced eight prominent political activists and opposition leaders to life in prison on Wednesday on charges of plotting a coup during protests in the kingdom earlier this year.

In all, 21 defendants, six of them tried in absentia, were charged with plotting to overthrow the government by force in collusion with a “terrorist organization” working for a foreign country. They can appeal the sentences.

UN Secretary-General Ban Ki-moon and the US State Department have also voiced alarm at the harsh sentences.

The protests demanded political reforms and an end to discrimination.

A Bahrain military court last week postponed the trial of 48 doctors arrested during the crackdown on dissent, after their lawyers said they had been tortured in custody.

“We understand that the trial of these medical professionals is to be held next week,” Pillay’s spokeswoman said.

Pillay, a former UN war crimes judge, is concerned at the continuing work of the Lower National Safety Court, as the king lifted a state of emergency on June 1, Shamdasani said.

The court has convicted more than 100 people since March this year, mostly for crimes they were accused of committing during the protests, she said. “We understand that in total, up to 1,000 people reportedly remain in prison,” she said.

“We call for an immediate cessation of trials of civilians in the court of national safety and an immediate release of peaceful demonstrators who were arrested in the context of the protest movement in February,” Shamdasani added.

Pillay’s office had cited worrying reports of mistreatment of detainees, including severe beatings of some of the defendants just sentenced, according to her spokeswoman.

“The government must urgently conduct an independent investigation into these allegations,” Shamdasani said.

Failing a credible independent national investigation, then an international probe should be conducted, she added.