Four Yemeni inmates released from the US Guantanamo Bay military prison in Cuba have landed in Saudi Arabia.
The news comes amid reports President Barack Obama is attempting to empty the facility as much as possible prior to Inauguration Day. With 34 days left in office, 59 prisoners remained.
All nine detainees were linked to al-Qaeda.
Trump said on Tuesday all of those held at Guantanamo should remain, despite lengthy inter-agency reviews that deemed many of them eligible for transfer.
The Pentagon said Gitmo transfers would continue over Trump's objection. The prisoners being transferred have been announced in parole-style hearings to be safe for repatriation or resettlement in other countries.
He tweeted that there should be no further releases from Guantanamo as the detainees are extremely unsafe people and should not be allowed back onto the battlefield.
Prisoners who will remain in Guantanamo Bay are those facing military charges or deemed too unsafe to transfer.
The incoming president pledged to keep the facility open and "load it up with some bad dudes". Around two dozen have not been charged but are deemed too unsafe to release. Because of the ongoing instability in that country, USA officials have been unable to repatriate them and have sought third-party countries like Saudi Arabia to take them in. "These are extremely risky people and should not be allowed back on the battlefield".
Last April, the Islamic kingdom - a top US ally in the Middle East - accepted nine Yemenis and put them through a Saudi government-run rehabilitation program that seeks to reintegrate militants into society.
Obama, who inherited 242 detainees at Guantanamo Bay when he took office in 2009 and has called it a "recruiting tool" for terrorists, has slowly whittled the number downward.
"Right now, we're planning to reduce the population and close this place down", the facility's Director of Public Affairs Capt. John Filostrat said.