WASHINGTON — The government transferred five low-level Guantánamo Bay prisoners to Eastern Europe on Thursday. Four of the men were Yemenis, and their resettlement was a significant policy change in the Obama administration’s effort to close the prison at the naval base in Cuba.

The United States sent one Yemeni and a Tunisian to Slovakia, and the three other Yemenis to Georgia. All five men had been held without trial and had been unanimously recommended for transfer, if security conditions could be met in the countries where they were to be sent, by an interagency task force in 2009.

The problem of what to do with a large number of low-level prisoners — those who are considered less of a threat — from Yemen has been seen as a major impediment to closing the prison. For years, officials in the Bush and the Obama administrations have been reluctant to repatriate Yemenis because of poor security conditions there. But they had also held out hope that matters would improve enough that low-level Yemenis could be repatriated.

As a result, even though large numbers of low-level detainees from other countries were sent home years ago, and dozens from other countries who could not be repatriated were resettled in nations that offered to take some in, most of the Yemenis have stayed imprisoned, eventually becoming a majority of the inmate population.