5 February 2012 Last updated at 16:34 ET
Egypt says it is to put on trial 43 people - including Americans and other foreigners - over the funding of non-governmental organisations.
Egypt's ruling military council has accused foreign groups of funding street protests against them.
It has raided the offices of several NGOs and banned a number of foreign staff from leaving the country.
Washington has warned it could review US aid to Egypt unless Cairo respects the rights of NGOs.
State department spokeswoman Victoria Nuland said the US was "deeply concerned by these reports" and was seeking "clarification" from the Egyptian government.
Campaign group Human Rights Watch called on the Egyptian government to drop the charges against the NGO workers.
"Foreign funding is their lifeline. Egypt's military government is now using the kind of tactics used by Zimbabwe and Ethiopia to silence independent voices," the group said.
The announcement came on a fourth day of violent street protests in Egypt amid anger at the authorities' perceived inability to prevent a riot at a football match last week that left 74 people dead.
Security forces fired tear gas at the thousands of rock-throwing protesters who were marching on the interior ministry in central Cairo.
Silencing critics?
Nineteen Americans are among those standing trial.
They are accused of "setting up branches of international organisations in Egypt without a license from the Egyptian government" and of "receiving illegal foreign funding," AFP news agency reports.
The son of US Transport Secretary Ray LaHood is believed to be among those facing criminal charges.
Sam LaHood heads the Egyptian office of the International Republican Institute (IRI) and was among several foreign workers banned from leaving Egypt just over a week ago.
The IRI and the National Democratic Institute (NDI), loosely associated with the US Republican and Democratic parties, were among 17 US-based and local foreign-funded groups whose offices were raided by prosecutors in late December.
Egyptian prosecutors said at the time they were acting on evidence suggesting some groups were violating Egyptian laws, including by not having permits.
But Cairo's action has widely been seen as an attack on free speech and an attempt by the Supreme Council of the Armed Forces' (SCAF) to silence critics of its attempt to put down ongoing street protests.
On Saturday, US Secretary of State Hillary Clinton reiterated Washington's warning that aid to Egypt - including $1.3bn of military assistance given each year - would be reviewed.
The Associated Press news agency says five Serbs, two Germans and three non-Egyptian Arab nationals are among those facing trial.
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