This picture taken on September 19 shows 'Diana' (using a pseudonym), who housed a 16-year-old boy for three months before he tried to flee Hong Kong by speedboat for Taiwan with 11 activists before getting caught by mainland Chinese authorities in August. The dozen, now known as the 'Hong Kong 12,' have since disappeared into the mainland's opaque and party-controlled justice system, compounding fears in Hong Kong that Beijing's authoritarianism is creeping into the finance hub. Photo: AFP / May James

Relatives of 12 Hong Kong democracy activists detained in mainland China said Friday that letters from their loved ones praising their treatment and urging their families to stay quiet about their plight were likely written under duress.

The hand-written letters from seven of the detainees are the first time families have heard directly from the group since they were arrested by the Chinese coast guard in late August trying to flee Hong Kong for Taiwan by speedboat.

In a statement, family members said the letters warned relatives against speaking to the media and seemed to adhere to a template.

“There were many letters that directly ‘responded’ to the doubts of the outside world about China,” the statement said. “It is doubtful that they wrote the letter out of their own free will,” they added.

Most of those on board the vessel were being prosecuted in Hong Kong for crimes linked to last year’s huge and often violent democracy protests.

They have since disappeared into the mainland’s notoriously opaque, party-controlled legal system on immigration charges where a conviction is all but guaranteed for those who go to trial.

The letters were passed by lawyers appointed by the Chinese government after family-appointed counsel were denied access to the detainees, a common move by authorities for sensitive or political cases. 

Four of the letters were provided to the media by “The 12 Hong Kongers Concern Group,” which has been helping the families of those detained. 

“I live very well here. Don’t worry about me. I’m very healthy and I’m full from three meals every day,” one letter from detainee Cheng Tsz-Ho, dated October 21, read.

“I sleep well, eat well and rest well here…. The [staff] of the detention center are very kind,” another letter from Tang Kai-yin, dated three days later, read.

Forced confessions, torture and lengthy incommunicado detentions have been well-documented inside mainland China’s legal system.

Semi-autonomous Hong Kong maintains an independent common-law legal system that has helped fuel its rise as a dependable global trade hub.

But Beijing is asserting increased control over the city after last year’s huge protests.