Signs of dissent have been rare during the Beijing Olympics
The US has asked China to release eight US activists held for mounting pro-Tibet rallies during the Olympics.
In a statement, the US embassy said it was "disappointed" China had not used the Olympics "to demonstrate greater tolerance and openness".
The authorities say the protesters will be freed by the end of the month.
Before the Games, the authorities said protests would be allowed in three designated areas, but it never approved any of the applications to use them.
And rights groups claimed that some people were arrested as they tried to apply for a permit.
Olympic chief Jacques Rogge said in a news conference that the failure to grant any licences to protest was unusual.
As well as eight US citizens, China's authorities also continue to hold a UK national.
The UK Foreign Office has already urged China to free 41-year-old Mandie McKeown, saying China needed "to respect its commitment to freedom of expression".
Beijing says the activists will be deported on 30 and 31 August.
Several other foreign protesters have already been deported.
Although the organisation of the Games has been widely praised, rights groups have criticised the Beijing government throughout.