Egypt is to try 44 people over the alleged illegal funding of aid groups, a judicial source said on Sunday, a day after Washington said it would review aid to Cairo over the crackdown.

"Forty-four people, including Egyptians, 19 Americans and other nationalities, have been referred to the Cairo criminal court in the NGO funding case," the source told AFP, adding that a travel ban on all remained in place.

The official MENA news agency said the group also includes Germans, Norwegians, Serbians, Jordanians and Palestinians.

German Foreign Minister Guido Westerwelle slammed the decision.

"It is unacceptable to harm organisations that have a real international mission which they take on seriously," he told ARD television according to an early release transcript

"We shall act, in the framework of our foreign policy towards Egypt, in such a way as to ensure that political organisations that have a worldwide reputation are allowed to continue working as they have done."

The aid workers are accused of "setting up branches of international organisations in Egypt without a license from the Egyptian government" and of "receiving illegal foreign funding."

The move comes amid what commentators say is a campaign to silence dissent.

Egypt's ruling military council, which took power after an uprising toppled veteran president Hosni Mubarak, has accused foreign groups of funding street protests against them.

The move will further strain US-Egypt ties after the offices of several non-governmental organisations, including US groups International Republican Institute, the National Democratic Institute and Freedom House, were raided.

In December, Cairo prosecutors stormed 17 offices of local and international NGOs, confiscating computers and paperwork as part of a probe into allegations of illegal foreign funding.

Egypt then barred some US members of the NGOs from leaving the country and American officials said "a handful" took refuge inside the US embassy.

On Saturday, US Secretary of State Hillary Clinton warned that Washington's aid to Egypt will be reviewed, highlighting the continued deadlock over Cairo's crackdown.

In a meeting with Egyptian Foreign Minister Mohamed Amr on the sidelines of the Munich Security Conference, Clinton said she "had a chance to once again express our deep concerns with what is happening to our NGOs."

"We do not believe there is any basis for these investigations, these raids..., the seizure of their equipment and certainly no basis for prohibiting the exit from the country by" NGO members, Clinton said.

"We are very clear that there are problems that arise from this situation that can impact all the rest of our relationship. We do not want that," she said.

"We have have worked very hard the last year to put into place financial assistance and other support for the economic and political reforms that are occurring in Egypt," she said.

"And we will have to closely review these matters as it comes time for us to certify whether or not any of these funds from our government can be made available under these circumstances," Clinton added.

Last week senior Egyptian military officers had visited the United States for talks in a bid to defuse the row.

US Defence Secretary Leon Panetta telephoned Egypt's military ruler, Field Marshal Hussein Tantawi, and asked him to lift the travel ban on the American citizens.

Among those barred from leaving the country is the Egypt director of IRI, Sam LaHood, the son of US Secretary for Transportation Ray LaHood.

Egypt's ruling military have accused "foreign hands" of sowing unrest in the country amid a spike in tensions between the military and activists who want a speedier transition to civilian rule.

The probe also coincided with Washington raising concerns with the ruling military about "anti-Americanism" in Egypt.

Egyptian officials told AFP the investigation was first launched in July by the ministry of international cooperation after the newly appointed US ambassador to Cairo, Anne Patterson, said the US distributed $40 million (35 million Euros) to NGOs since Mubarak's fall.

The military enjoys close ties with Washington and receives more than $1 billion in US aid annually.