The Washington Post is reporting that at least four Americans are being held in Yemen by rebels who toppled the US-backed government.
The report cites unnamed sources who say that the Americans are believed to be imprisoned in the capital Sanaa.
Saudi Arabia has repeatedly bombed the city in a campaign to oust the Shiite rebels, known as Houthis, from power.
The sources say that attempts to free the Americans have failed.
The report says none of the Americans held is a US government employee.
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Three of the prisoners held private sector jobs, and the fourth holds dual US-Yemini citizenship.
The Post report says the newspaper is withholding details about the four, at the request of relatives and US officials who cited safety concerns.
