A video has surfaced online showing the wife of Liu Xiaobo for the first time since the funeral of the Nobel Peace Prize laureate, who died in Chinese custody last month.

The video shows Liu's widow, Liu Xia, saying in a hoarse voice that she hopes her friends will give her space to grieve.

The clip, which was posted on YouTube late on Friday without any indication of where or when the footage was taken, quickly drew criticism from the couple's supporters yesterday that it looked staged by Liu's minders.

“Please give me time to mourn and time for my heart to be restored,” said Liu Xia, speaking while seated on a couch dressed in a dark sweater and pants and smoking a cigarette.

“When Xiaobo was alive, the doctors did their best and Xiaobo regarded life and death as being very ordinary, so I have to also try hard to adjust myself,” she said. “And in the future, when I'm better in various ways, I will be with you all again.”

An accomplished poet and artist, Liu Xia was never charged but has been kept guarded and largely isolated for more than seven years in the apartment she once shared with her husband.

She remains unreachable, raising concerns among Western governments, the UN and her supporters that she is unable to move freely or leave the country if she chooses to do so.

Liu Xia's body language appeared to show that she was speaking to the person holding the camera with some formality, said Zeng Jinyang, a Hong Kong-based documentary maker and a supporter of the couple.

“You can tell from her body language that this is not a close relationship and the atmosphere in which she speaks is one that is not relaxed,” Ms Zeng said by phone. “Liu Xia's speaking style also tends to be fragmented. This message is very clearly scripted, which is not her style.”

Liu Xiaobo died on 13 July in Chinese custody after a battle with liver cancer, amid international criticism of Beijing for not letting him travel abroad as he had wished.

Liu was only the second Nobel Peace Prize winner to die in police custody, a fact pointed to by human rights groups as an indication of the Chinese Communist Party's increasingly hard line against its critics. The first, Carl von Ossietzky, died from tuberculosis in Germany in 1938 while serving a sentence for opposing Adolf Hitler's Nazi regime.