Egyptian authorities have slapped a travel ban on several US citizens working for non-governmental organisations, preventing them from leaving the country, officials said on Thursday.
"We understand that a number of Americans working for NGOs, including the IRI, have been barred from travelling," US Assistant Secretary of State for Democracy and Human Rights Michael Posner said in Cairo.
The IRI is the International Republican Institute, whose Egypt director Sam LaHood -- the son of US Secretary for Transportation Ray LaHood -- was among those banned from travel, an Egyptian airport official said.
The ban was issued following "the orders of the prosecutor general," the official told AFP.
In Washington, State Department spokeswoman Victoria Nuland said she believed "four or five" Americans had been prevented from taking flights from the airport, although she added their passports had not been confiscated.
Nuland told reporters she understood that the ban will last as long as it takes for the Egyptian authorities to complete a judicial process.
"We are urging the government of Egypt to lift these restrictions immediately and allow folks to come home as soon as possible. And we are hopeful that this issue will be resolved in a few days," Nuland said.
The move comes amid a crackdown on foreign-funded NGOs.
It is likely to further strain relations between Egypt and the United States after prosecutors last month stormed the offices of groups including IRI as part of a probe into allegations of illegal funding from abroad.
Nuland said the authorities have yet to return computers and other confiscated material, which she added are also subject to the ongoing judicial process.
Posner said the United States was "gravely concerned that organisations like IRI and like NDI (the National Democratic Institute) and Freedom House which have long worked in this country and around the world, are not able to operate as they do in many places in the world."
NGOs "need to have the ability to operate openly, freely, without constraints," said Posner, who discussed the matter with officials in Egypt.
The raids in December came after an order from judges tasked with investigating the groups' foreign funding.
The groups allegedly did not obtain licences to operate or permission from the foreign and social solidarity ministries, the prosecutor general's office had said in a statement.
The probe, which began last summer, coincided with Washington raising concerns with the ruling military about "anti-Americanism" in Egypt.
A cabinet source had 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 to NGOs since Mubarak's ouster in February.