China on Friday blasted an award given in the US to an exiled Uighur dissident as a "blasphemy against and a stain upon human rights", as President Xi Jinping visited Washington.

Xi, who was in Washington for the Nuclear Security Summit, met his US counterpart Barack Obama on Thursday amid tensions between the world's two biggest economies over the South China Sea, cyber security, rights and other issues.

A day earlier the Washington-based Victims of Communism Memorial Foundation (VOC) gave Dolkun Isa, an activist from China's Xinjiang region, an award for "his dedicated human rights advocacy".

Xinjiang is home to the mostly Muslim Uighur minority, many of whom say they face cultural and religious repression, and the area is regularly hit by violence which Beijing blames on Islamist separatists.

"That an organisation would give a terrorist like Dolkun with such an extensive criminal record an award is blasphemy against and a stain upon human rights and the rule of law, and also makes a mockery of them," Chinese foreign ministry spokesman Hong Lei told a regular briefing Friday.

Isa is now a German citizen and chairman of the Munich-based World Uighur Congress, which advocates for the rights of Chinese Uighurs around the globe.

Hong said he was "a red-level target wanted by Interpol and the Chinese police for his organisation and implementation of numerous bombings, robberies, killings and other serious criminal offences and violent acts", which Isa denies.

"These accusations are made to discredit my work," he said, adding that Beijing's policies had left Uighurs living in "a climate of fear and helplessness".

"I firmly advocate for a peaceful resolution to the Uighur issue and reject violence, and this threatens China," he said.

In his acceptance speech Wednesday, Isa acknowledged that the Chinese government saw him as a "terrorist" and had issued a warrant through Interpol for his arrest, leaving him unable to enter countries "vulnerable to Chinese pressure".

VOC executive director Marion Smith hailed Isa as a "proud addition to the ranks of world leaders" in a statement.

According to its mission statement, VOC seeks to "memorialise, educate and document the grim legacy of communism around the world". On its website, it solicits donations to help "put communism on the ash heap of history".

Over the past two years, Beijing has carried out a "strike hard" campaign in Xinjiang aimed at stopping unrest that has claimed hundreds of lives. Scores of people have been sentenced to death, while hundreds have been jailed or detained on terror-related offences.