BEIJING (AFP) - Chinese authorities have barred five European diplomats from visiting the widow of the late Nobel laureate dissident Liu Xiaobo, diplomatic sources said on Sunday (May 13).

Ms Liu Xia, 57, has been under de facto house arrest despite facing no charges ever since her husband was awarded the Nobel Peace Prize in 2010, a recognition that deeply angered the communist regime.

Mr Liu Xiaobo died of cancer last year while still in prison after being convicted of "subversion", making him the first Nobel laureate to die in custody since the era of Nazi Germany.

The diplomats' visit came following increased concern in recent days about Ms Liu Xia's psychological health.

The envoys, including a French and a German envoy, tried to visit her home on Friday morning, but were turned away by officials at the gate to the complex, the sources said.

The guards checked the diplomats' identities before refusing them entry without giving a reason.

Despite the daily restrictions and surveillance faced by Ms Liu Xia, Chinese authorities still maintain she is free.

Earlier this month, reports emerged that Ms Liu Xia had told friends she was ready to "die at home" in protest at her continuing detention by Chinese authorities.

Ms Liu Xia's friends have told AFP she is taking medication for depression and has suffered from heart problems and fainting.

AFP reporters have tried to visit Ms Liu's home multiple times in recent years, but were blocked each time by plainclothes men.

The United States and European Union have called on President Xi Jinping's government to free the widow and let her travel abroad.

Germany's ambassador to China previously told the Hong Kong-based South China Morning Post that Ms Liu would be welcomed in his country.

When asked earlier this month about western diplomatic calls for Ms Liu Xia to travel abroad, Foreign Ministry spokeswoman Hua Chunying told reporters: "But Liu Xia is a Chinese citizen. The relevant Chinese authorities will handle relevant issues in accordance with the law."

Mr Liu Xiaobo was a veteran of the 1989 Tiananmen Square protests and was detained in 2008 after co-authoring Charter 08, a petition calling for democratic reforms.

He was sentenced to 11 years in prison for "subversion", but died in custody last July after authorities rejected his request to receive treatment abroad.