The Donetsk-based monitoring group, comprised of four people from Estonia, Switzerland, Turkey and Denmark, was reportedly detained by a pro-Russian separatist group identifying itself as the Sloviansk self-defense forces on May 26.
They were freed on Thursday and were reportedly "in good condition," the OSCE noted in a statement.
A second team of abducted monitors has not yet been released. OSCE lost contact with four monitors and a translator on May 29 after the group was taken by armed separatists in Luhansk, a stronghold of the pro-Russian resistance.
The OSCE noted that "intense efforts have been taken on all levels to seek the immediate and unconditional release of the monitors."
The monitors are part of the OSCE Special Monitoring Mission to Ukraine. Despite the abductions in Ukraine's restive eastern region, the OSCE said that "monitors remain and continue working in Donetsk and Luhansk." The OSCE added, however, that teams have been reconfigured and the number of monitors in those two regions reduced in light of security concerns.