More than half the pro-democracy activists awaiting trial in Egypt come from outside the country, human rights groups have warned, raising fears that the military is deliberately targeting foreigners.

The Egyptian military's decision to prosecute 19 American and 10 other non-national pro-democracy activists has led to cries of an unfair focus on activists from overseas in a probe into illegal funding of aid groups. One of the Americans is the son of a US government official.

A total of 43 people are facing trial. Five Serbs, two Germans and three non-Egyptian Arab nationals are also among those referred to trial, AP reported.

Critics of the Supreme Council of the Armed Forces (SCAF) said that internal groups such as the Muslim Brotherhood and Sunni Islamic Salafi organisations have not been investigated.

A source close to the government told the Egyptian Al-Masry Al-Youm that internal groups were not investigated because no one filed a complaint accusing them of accepting foreign funding.

"The report of the fact-finding committee, organised by the former justice minister, as well as a report prepared by planning and international cooperation minister Fayza Abouelnaga offered no grounds for investigating these groups," the source said.

Other sources claimed that while Salafi-oriented group Ansar al-Sunnah and the foundation set up by Mohamed Alaa Mubarak, the grandson of ousted president Hosni Mubarak, were originally also under investigation, the judges did not bring any charges against them.

Security forces raided the offices of 17 local and international NGOs in December as part of a probe into illegal funding.

The government has accused the aid workers, who have been banned from travelling, of setting up branches of international organisations in Egypt without a licence from the government and of receiving illegal foreign funding.

US State Department spokeswoman Victoria Nuland said: "We are deeply concerned by these reports and are seeking clarification from the government of Egypt."

Sam LaHood, the head of the Egypt office of the Washington-based International Republican Institute and the son of US transportation secretary Ray LaHood, will be among the aid workers to be prosecuted.