Five detainees from the controversial U.S. detention facility in Guantanamo Bay, Cuba, were released Wednesday, after over 12 years of incarceration, multiple media reports confirm.

Four of the five men, who are all from Yemen, will be sent to Oman, and one will be sent to Estonia -- marking the first time that either country has agreed to accept former prisoners from the facility, the Associated Press reported.

The men, who are all in their 30s and 40s had been cleared for release since 2009, but U.S. officials declined to return them to their native country Yemen, where the government has been engaged in a conflict with al Qaeda-affiliated groups in recent years, the BBC reported.

According to U.S. military documents released by Wikileaks, the men, Al Khadr Abdallah Muhammad Al Yafi, Fadel Hussein Saleh Hentif, Abd Al-Rahman Abdullah Au Shabati, Mohammed Ahmed Salam and Akhmed Abdul Qadir, were all suspected of having ties to al Qaeda, but much of the information linking them to the group had proved inaccurate, U.S. officials cited by the Washington Post reportedly said.

The U.S. banned the return of Yemeni detainees to the country in 2009, after Omar Farouk Abdelmuttab attempted to blow up a plane over Detroit, in a plot involving al Qaeda in the Arabian Peninsula, the group's Yemeni branch, CBS News reported.

The detainees' freeing is the latest in a series of releases from the prison, and brings the facility's inmate population down to 122. Previously, the prison housed over 800 inmates, detained by U.S. forces during military operations launched as a result of the 9/11 attacks.

President Barack Obama vowed to close the Guantanamo detention facility when he took office, and signed an executive order instructing its closure immediately after he came to power. However, restrictions passed by Congress have stymied attempts to close the controversial facility, and the administration has struggled to find an acceptable formula to resolve the cases of many detainees, some of whom have been held without charge for over a decade.

A bill tabled by Republican senators this week seeks to curb the president's powers to release Guantanamo inmates. Lawmakers proposing the bill cited the recent terrorist attacks in Paris as justification for the move, the Washington Post reported.

In response to the legislative push, the Obama administration suggested this week the number of former Guantanamo detainees who have gone on to become involved in terrorism was far smaller than Republican lawmakers claimed, the Los Angeles Times reported.