The U.S. Defense Department transferred five more prisoners from Guantanamo Bay on Tuesday, part of a recent string of releases as President Barack Obama hurries to fulfill his promise of closing the prison.

Three Yemeni and two Tunisian prisoners were transferred to Kazakhstan in Central Asia, the Pentagon said according to Voice of America.

The prisoners, held at the Cuba-based prison for 11 years, were all detained in Pakistan on suspicion of having links to al-Qaeda and other Islamist extremist groups.

They were never charged for any crime and were eventually cleared for release, but like other prisoners, they were not released due to a U.S. law prohibiting detainees from being transferred to the U.S.

Other obstacles include trying to secure countries to take the prisoners and security concerns over sending them back home.

In this situation, the U.S. has not specified why the five men could not be sent home, but officials have been reluctant to send Yemenis back due to rebel activity, Fox News reported. Some Tunisians are afraid of persecution.

A total of 127 detainees now remain at Guantanamo. Close to 30 prisoners have been released this year to countries including Uruguay and Afghanistan.

Reducing the number of prisoners to less than 100 could give the Obama administration leverage to convince Congress to allow the base to shutdown, since maintaining each prisoner costs a whopping $2.7 million a year, the Wall Street Journal previously reported.

"As the number becomes smaller at Guantanamo, the case for domestic transfers becomes that much stronger," a senior administration official told the newspaper in October.

The latest freed prisoners have been identified as Asim Thabit Abdullah al-Khalaqi, Muhammad Ali Husayn Khanayna and Sabri Muhammad, all from Yemen, VOA reported.

The last two are Adel al-Hakeemy and Abdullah Bin Ali al-Lufti, both from Tunisia.