President of Ethiopia's Somali region Abdullahi Hassan refused to give exact numbers of those detained.

"Those who are waging the terrorist war against our people are coming from Europe, are coming from America," he told journalists.

A rebel group is fighting for more autonomy for the Somali region.

Mr Hassan said people originally from the region, also known as the Ogaden, were raising money for the rebel Ogaden National Liberation Front (ONLF).

"They are buying with this money weapons, mines and explosives," he said.

An ONLF spokesman denied the claims.

Abdirahman Mahdi told the BBC News website that hundreds of ONLF members were in prison at the moment but said none of them had foreign passports.

'Facing trial'

US embassy spokeswoman in Addis Ababa Darragh Paradiso said:

"We have no information on American citizens being detained and are following up on this issue with the government of Ethiopia as we speak."

Mr Hassan said he did not care whether foreign diplomats got involved in the cases.

"They are under Ethiopian law, they are facing trial."

He said they were under detention in the regional capital, Jijiga.

The conflict in the region has escalated since last April, when the ONLF attacked a Chinese-run oilfield, killing 74 people.

Aid workers are concerned about hunger in the remote, arid area after commercial food deliveries were blocked for several months.

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