The US embassy in Beijing urged China on Tuesday to lift any restrictions on the wife of jailed dissident Liu Xiaobo, the winner of the Nobel Peace Prize whose award has stirred tensions over human rights.
Liu is serving 11 years in jail on subversion charges for demanding democratic transformation of China's one-party state, and his wife Liu Xia has sent out messages she is under house arrest in Beijing, according to news reports and overseas human rights groups.
A spokesman for the US embassy in the Chinese capital, Richard Buangan, added to calls for any fetters on Liu Xia to be lifted.
"We remain concerned by multiple reports that Liu Xia is being confined to her home in Beijing," he said in an email.
"Her rights should be respected, and she should be allowed to move freely without harassment," he said, adding that China should "uphold its international human rights obligations".
China's ruling Communist Party has long reacted angrily to pressure over its restrictions on political and legal rights of citizens, and the Nobel Prize for the prominent dissident has prompted testy official and vehement media comment in Beijing.
The Party is holding a high-level meeting from Friday that will add to leaders' jitters over control of potential protests.
China has also condemned the Norwegian government, which has no say over the prize, and cancelled a planned meeting with a Norwegian fisheries minister.
Diplomats from the European Union as well as Australia and Switzerland unsuccessfully tried to visit Liu Xia in her apartment in western Beijing on Monday but were blocked.