Six Guantanamo detainees have been transferred to Uruguay from the American military base in Cuba, where 136 detainees remain, the Pentagon said Sunday.

Among the inmates transferred was Syrian prisoner Jihad Diyab, 43, who had staged a hunger strike and requested a US court to order prison officials to stop force-feeding him.

The six men -- including three other Syrians, a Palestinian and a Tunisian -- received an "approved for transfer" from US authorities and left the military base on a US Air Force plane at 12:00 am (0500 GMT) Sunday, Pentagon spokesman Myles Caggins told AFP.

There are still 136 prisoners at Guantanamo, most of whom are detained without charge or facing trial. Sixty-seven of them have been approved for release by the successive governments of George W. Bush and Barack Obama.

Sunday's transfers follow the release of seven prisoners in November.

"We are very grateful to Uruguay for this important humanitarian action, and to President (Jose) Mujica for his strong leadership in providing a home for individuals who cannot return to their own countries," special envoy for Guantanamo closure Cliff Sloan told AFP.

"The support we are receiving from our friends and allies is critical to achieving our shared goal of closing Guantanamo, and this transfer is a major milestone in our efforts to close the facility."

The men arrived in Uruguay on Sunday morning and were taken to a military hospital for exams, reported weekly newspaper Busqueda, which first broke the story of the negotiations for their transfer.

Uruguay's leftist President Jose Mujica announced in March that the South American country would take in the inmates on humanitarian grounds in an effort to help US President Barack Obama fulfill his long-delayed promise to close the military prison in Cuba.

The transfers, initially to take place last August, were delayed for political reasons.

By the time Washington was ready, Uruguay was in the midst of an election campaign to choose Mujica's successor, making the issue a political hot potato.

But after his Broad Front (FA) party secured another five years in power with the election of his ally Tabare Vazquez in a runoff election last Sunday, Mujica pressed ahead with the deal.

- 779 prisoners, 13 years -

A total of 779 prisoners have been held at Guantanamo in the nearly 13 years since the military detention center was set up in the wake of the September 11, 2001 attacks.

The Pentagon named the six released Sunday as Syrians Ahmed Ahjam, Ali Hussein Shaabaan, Omar Abou Faraj and Jihad Diyab; Palestinian Mohammed Tahanmatan; and Tunisian Abdoul Ourgy.

They are all aged between 30 and 40 years old and were among the first detainees to arrive in Guantanamo in 2002, said the Pentagon.

Diyab is one of several prisoners who have staged hunger strikes at Guantanamo arguing that they are being held in legal limbo.

Last year, Guantanamo prisoners staged the largest protest in the prison's history -- involving two-thirds of all detainees at its peak and spanning six months.

At least 46 have been fed intravenously by prison officials who justify the practice on medical grounds and filmed the feedings.

A federal judge has ordered the redacted release of the videotapes, but granted a request by President Barack Obama's administration for a pause on releasing them. The government is expected to appeal the release order.

The closure of the prison, set up to hold detainees from President George W. Bush's post-9/11 "War on Terror," was a prominent part of Obama's election campaign in 2008.

Yet attempts to realize his ambition have been thwarted by domestic and international obstacles, leaving the fate of the jail and its prisoners in limbo.

In Uruguay, the six transferred prisoners will live as free men and have the same liberties as any resident, including the right to travel, Mujica has said.

The Pentagon's envoy for the closure of Guantanamo, Paul Lewis, said he always visits countries where detainees may be sent before a final decision on a transfer is taken.

"Security is always top-of-mind prior to any decision to transfer a detainee, and each detainee is closely reviewed by six departments before he is eligible for transfer," he said.

Mujica, a former guerrilla known for legalizing marijuana, giving most of his salary to charity and living in a run-down farmhouse, has said he sympathizes with the transferred inmates because of the 13 years he spent as a political prisoner.