Egypt - The United States demanded "clarification" over Cairo's apparent plans to put dozens of pro-democracy activists, including 19 Americans, on trial over charges of illegal funding of aid groups.

US State Department spokeswoman Victoria Nuland said Washington was "deeply concerned" over the developments, which threatened to further strain ties with Egypt's post-Arab Spring military rulers.

A top official at Freedom House, one of the groups targeted, called Egypt's handling of the matter "a disaster."

A judicial source in Cairo told AFP 44 people, including Egyptians, would be tried over alleged illegal funding of aid groups, a day after the United States said it would review aid to Egypt, $1.3 billion last year, over the crackdown.

"We have seen media reports that judicial officials in Egypt intend to forward a number of cases involving US-funded NGOs to the Cairo criminal court," Nuland told reporters traveling with Secretary of State Hillary Clinton.

"We are deeply concerned by these reports and are seeking clarification from the government of Egypt."

The offices of Freedom House and the International Republican Institute were among 17 local and international NGOs raided in December by Egyptian authorities as part of a probe into alleged illegal funding.

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

A travel ban on all the NGO workers who were detained remains in place.

The decision to try the foreign workers comes as Egypt remains beset by unrest sparked by the perceived failure of its military rulers and police to prevent football-linked violence following a match in the northern city of Port Said on Wednesday that left 74 people dead.