Egyptian security forces have launched raids on a series of high-profile human rights and pro-democracy organisations based in Cairo, including the US National Democratic Institute, founded by former secretary of state Madeleine Albright, and the International Republican Institute.
During the raids riot police confined staff to their offices and forbid them from making phone calls. About half a dozen Egyptian and international groups were targeted as part of a widespread investigation into foreign funding of Egyptian civic society groups.
The raids on NDI and IRI, however, both of which have received US state department funding for their operations, will be bound to cause friction with the US government, which underwrites military aid to Egypt to the sum of $1.3bn (£843m) annually.
In recent months, the Supreme Council of the Armed Forces has accused local non-governmental organisations of receiving money from abroad, and has argued that the recent unrest in the country is by "foreign hands".
Hana el-Hattab, an NDI staffer trapped inside her office, tweeted: "We're literally locked in. I really have no idea why they are holding us inside and confiscating our personal laptops." In other tweets she wrote: "I was on the balcony, dude with machine gun came up and told us to go in and locked it ... we asked if they had a search warrant,they said the person who issues warrants is in building &doesn't need to issue one for himself. They're even taking history books from people's bags."
Heba Morayef, who works with Human Rights Watch in Egypt, said she had received a message from an NDI staffer confirming they had been confined inside their offices by riot police. Images posted on Twitter showed armed police in body armour stationed outside.
Security forces, both uniformed and plainclothes, forced their way into the offices where employees were informed that they were under investigation by the public prosecutor.
According to witnesses, laptops and other documents were also seized during the raids.
The raids follow a far-reaching investigation into the foreign funding of human rights and civic advocacy groups launched under the aegis of the country's ruling generals earlier this year.
Ironically, the law being used to pursue the groups is one from the era of former president Hosni Mubarak, which the government had said it intended to repeal.
During the Mubarak era, groups such as NDI and IRI and others had existed in a grey area, unable to obtain permission to operate in full legal compliance.
Other groups reportedly raided, say activists, include the Konrad Adenauer-Stiftung, which supports political dialogue, Freedom House and the Egyptian Public Budget Observatory.
Morayef condemned the raids, and the investigation that led to them, as "entirely inappropriate" adding: "This is part of a wider crackdown on civil society groups in Egypt using Mubarak-era laws.
"They are using these pre-revolution laws as a broadbrush investigation that could result in wholesale shutting down of human rights and other groups that have been at the forefront of criticism of the army.
"This is very selective and really, really serious. It has huge potential implications for human rights in Egypt."
The Cairo Institute for Human Rights Studies said: "The NDI, IRI and Freedom House have been previously investigated by the ministry of justice on charges of receiving foreign funding, while the Arab Centre for the Independence of Justice and Legal Professions has not been yet investigated."
The army has pledged to step aside by mid-2012. "In Mubarak's time the government never dared to do such a thing," said prominent human rights activists Negad el-Bourai on his Twitter account.
Political experts said the groups raided on Thursday have taken a neutral political stance, focusing on fostering democracy in Egypt by training members of nascent parties. "The National Democratic Institute has been training new parties ... in how to participate in elections," a leading member of a liberal party said on condition of anonymity.
"This has been with the full knowledge of authorities and was not clandestine."