The Nigerian suspect in that case had studied Arabic in the Yemeni capital, Sanaa.

Later a Yemen-based arm of al-Qaeda, Al Qaeda in the Arabian Peninsula, claimed responsibility for the attempted bombing.

Instability

The case has raised warnings from Western intelligence agencies and Saudi Arabia who say that al-Qaeda is trying to exploit instability in Yemen to use the country as a base to launch attacks in the region and beyond.

Citing Yemeni security sources, Monday's report in al-Hayat said one of those detained in the recent spate of arrests was a 24-year-old French man who travelled to Yemen in October from Egypt to study Arabic, even though he was fluent in the language.

Last Wednesday, Yemeni security officials were quoted as saying they had detained several foreigners, including Americans, Britons and an Australian woman, in connection with an investigation into al-Qaeda's increased activity in the country.

The two officials said some of those detained were believed to have links to the suspect in December's attempted aircraft bombing.

'Great cooperation'

In Washington, P.J. Crowley, spokesman for the US State Department, confirmed Yemeni authorities had 12 US citizens in custody and said officials were seeking more information about the individuals being held.

Asked if the US had provided information that led to the detention of the 12 he said the Washington had "great cooperation with the government of Yemen."

"Together, we are doing our best to help Yemen ... reduce the threat posed by al-Qaeda in the Arabian Peninsula," he said.

"That's a threat to Yemen. It's a threat to the United States. But beyond that, I'm not going to talk about specifics."

In recent months the US defence department has approved spending $155m to aid Yemeni security forces, including the purchase of four helicopters to support operations against suspected al-Qaeda fighters.

The money also includes $34.5m to train and equip the Yemeni special forces and another $38m for aircraft to allow those forces quicker access to hotspots in the country.