The Chinese Embassy to the UK expressed "strong indignation" at an open letter pleading to release Ilham Tohti, read a statement published in the Guardian on Wednesday.

"The letter attempts to distort facts, exonerate suspected criminal activities and interfere with China's judicial sovereignty and independence," wrote embassy spokesperson Miao Deyu in the statement.

The "misleading letter" was published in the Guardian on April 27. Written by 50 members of the PEN American Center, it urged Chinese authorities to release and drop all charges against Tohti, who they claimed to be "working peacefully to build bridges" between Han and Uyghur people.

Police in Urumqi, capital of Northwest China's Xinjiang Uyghur Autonomous Region, announced in January that Tohti, a former lecturer at the Minzu University of China, had been arrested for alleged separatism. He reportedly has a close relationship with the World Uyghur Congress, which supports the "independence of Xinjiang," and the police said he has connections with overseas terrorist group East Turkestan Islamic Movement.

The embassy said in the statement that China protects the legitimate rights and interests of Uyghur compatriots and people of all ethnic groups, and that Tohti's case is being handled in line with the law.

"As any other sovereign state, China is duty-bound to tackle illicit and criminal activities according to its law. China's judicial sovereignty and independence brook no interference by any organization or individual," it read.