Image caption Liu Xiaobo, left, is in jail and his wife Liu Xia is under house arrest

US Secretary of State John Kerry has urged China to release Nobel Peace laureate Liu Xiaobo.

The remarks came in a statement marking five years since the activist was detained for subversion.

Mr Kerry also asked that Mr Liu's wife Liu Xia, who has been under house arrest since 2010, be released. Friends say she is suffering from depression.

Mr Liu was convicted of subversion in 2009. He won the Nobel the next year despite fierce opposition from China.

In a statement released on Monday, Mr Kerry said the US was "deeply concerned" that Chinese officials continued to detain Liu Xiaobo and other activists "for peacefully exercising their universal right to freedom of expression".

"We strongly urge Chinese authorities to release Liu Xiaobo, to end Liu Xia's house arrest, and to guarantee to Liu Xiaobo and his family members all internationally recognised human rights protections and freedoms," the statement said.

"We continue to believe that respect for international human rights is critical to China's growth, prosperity, and long-term stability," it added.

China's Foreign Ministry, however, stressed on Tuesday that the couple had "violated Chinese laws" and were "to be punished by Chinese laws".

"I want to suggest that only the 1.3 billion Chinese people have a say on China's human rights," spokesman Hong Lei said.

"We hope the US can bear in mind the overall interests of bilateral relations and do more things that are conducive to a bilateral relationship."

Liu Xiaobo was detained in 2008 and jailed the next year for his role in drafting a manifesto - Charter 08 - calling for political change.

He is currently serving 11 years in jail for inciting the subversion of state power.