The US on Thursday transferred four Yemeni detainees held at the notorious naval facility at Guantanamo Bay in Cuba as part of President Barack Obama's plans to reduce the prison population before he leaves office.

The detainees were met by family members in Saudi Arabia's capital Riyadh, where they are expected to go through a government-run deradicalization program.

After Thursday's transfer, at least 55 prisoners remain at the controversial detention facility, 10 of which face charges in military tribunals, including the alleged plotters of attacks committed on September 11, 2001.

Mohammed Bawazir, one of the prisoners released Thursday, protested his indefinite detention by staging a lengthy hunger strike, prompting authorities to force-feed him. In 2009, a federal court ruled that the force feeding procedure did not constitute torture.

Approximately 40 prisoners will remain at the detention center if the Obama administration is able to release those cleared for transfer.

However, it falls short of the outgoing president's campaign promise to close the Guantanamo facility.

'No further releases'

President-elect Donald Trump has vowed to keep the detention center open and "load it up with some bad dudes."

"There should be no further releases from Gitmo," the incoming president said in a tweet on Tuesday, referring to the facility. "These are extremely dangerous people and should not be allowed back onto the battlefield."

But White House spokesman Josh Earnest on Thursday said that the US will likely transfer additional prisoners before President-elect Donald Trump's inauguration.

"I am not able to speak to any specific detainee transfers between now and January 20 other than to confirm for you that there are likely to be some," said Earnest said.

ls/kl (Reuters, AFP, AP)