The Organisation for Security and Cooperation in Europe (OSCE) said on Saturday that pro-Russian rebels in eastern Ukraine have released four of the group's monitors they had detained at the end of May.
Unidentified freed OSCE observers arrive at a hotel in Donetsk early on June 27, 2014
"Our Lugansk-based team of 4 monitors have been released after 1 month in captivity. Details to follow," the OSCE Special Monitoring Mission to Ukraine said on its Facebook page.
Two groups of unarmed observers from the Vienna-based European security organisation -- totalling eight international monitors and a Ukrainian translator -- were detained at roadblocks three days apart in late May.
Separatist leaders on Thursday freed the group they had detained on May 26 in the Donetsk region.
But the second team seized on May 29 in the neighbouring Lugansk province appeared to have been abducted by a different militia and negotiations for their release intensified in the recent days.
A Donetsk rebel spokeswoman told AFP that the second team would be presented to reporters at a local hotel later on Saturday.
Russian President Vladimir Putin publically called on the pro-Kremlin militia to free all people held against their will under the terms of a temporary ceasefire in the nearly three-month insurgency agreed with Kiev at the end of last week.
Ukrainian President Petro Poroshenko extended the truce on Saturday morning until 1900 GMT Monday.