Image copyright AFP Image caption President Obama has vowed to close the Guantanamo Bay facility

Six Yemeni prisoners held for years at Guantanamo Bay detention centre have been transferred to Oman, the US says.

The departures from the prison in Cuba were the first for six months.

President Barack Obama promised to close Guantanamo Bay during his election campaign in 2008. Although he has been unable to do so, he has cut the number of inmates by half.

The latest transfers bring the number of detainees in Guantanamo to 116.

The men had been cleared to leave for years, but could not be sent back to Yemen because of the country's instability.

Congress has barred transfers to the US mainland, so the only option left for the authorities is to send prisoners to third countries.

Hunger strikes

In a statement, the Pentagon said the US was "grateful to the government of Oman for its humanitarian gesture and willingness to support ongoing US efforts to close the Guantanamo Bay detention facility".

It is the second transfer of Guantanamo prisoners this year, after the Pentagon announced in January that four men had been moved to Oman and one to Estonia.

The six Yemenis flown to Oman on Friday were identified by the Pentagon as Idris Ahmad Abd Al Qadir Idris, Sharaf Ahmad Muhammad Masud, Jalal Salam Awad Awad, Saad Nasser Moqbil Al Azani, Emad Abdallah Hassan and Muhammad Ali Salem Al Zarnuki.

Emad Abdullah Hassan has held repeated hunger strikes in protest against his confinement without charge since 2002.

Correspondents say that President Obama, thwarted by Congress in his efforts to close the prison, has had to rely on only a handful of countries that have agreed to accept detainees.

Last year, 14 detainees were transferred out of the prison, based at a US naval base in south-eastern Cuba.