The US government says six men held more than 12 years at Guantanamo Bay have arrived in Uruguay to be resettled as refugees.

The release of four Syrians, a Tunisian and a Palestinian, who arrived in South America aboard a US military transport plane on Sunday, represented the largest single group to leave the internationally condemned US detention camp since 2009, US officials said.

All six had been detained for suspected ties to al-Qaeda but were never charged.

A Pentagon statement on Sunday identified the men as Jihad Diyab, Ahmed Adnan Ahjam, Ali Hussain Shaabaan and Omar Mahmoud Faraj from Syria, Abdul Bin Mohammed Abis Ourjy from Tunisia and Mohammed Tahanmatan from Palestine.

Jose Mujica, Uruguaya's outgoing president, agreed to accept the men earlier this year as refugees but the transfer was delayed until after the country's presidential election.

Mujica, who has called Guantanamo a "disgrace", restated in an interview aired on Friday that he had rejected a US proposal to ban the detainees from travelling for two years after their release from Guantanamo.

"They are coming as refugees and the first day that they want to leave, they can leave," he said in an interview with state television that was posted on YouTube.

A US official said Uruguay agreed to "security arrangements" and that the six would be "free men." He declined to say whether they would be allowed to travel abroad.

Uruguay's president-elect, the ruling party's Tabare Vazquez, who assumes power on March 1, has said he also supports hosting the men as a humanitarian gesture.

The Uruguayan Foreign Ministry said in a statement on Sunday that it would adhere to international rules on humanitarian protection.

Their release brings the total number of prisoners at Guantanamo to 136 - the lowest number since the first month the prison opened in January 2002.

Seven other prisoners have been transferred from Guantanamo since early November, including three to Georgia, two to Slovakia, one to Saudi Arabia and one to Kuwait.

Notes from the Field

Daniel Schweimler in Montevideo

The Uruguayan Defence Minister, Eleuterio Fernandez Huidobro, said as soon the men had been passed fit and healthy they'd be free to live ordinary lives without restrictions. That, he said, may take a few days.

The weakest of the former detainees, Syrian Abu Wa'el Dhiab, who had been on hunger strike to protest his treatment, is now eating solids. It's not clear at this stage when he'll be leaving hospital.

Another of the four Syrians, Abdelhadi Omar Faraj, sent a letter, via his lawyer, to Uruguay's leading newspaper, El Pais, thanking the Uruguayan people and President Jose Mujica, for accepting them. "Without the goodwill of the Uruguayan people," he wrote, "we'd still be in the black hole of Guantanamo."

He confessed to being an ardent fan of Uruguay's national football/soccer team which he said he'd be supporting at the next World Cup.