Rebels in southeastern Ukraine early on Friday released four of the eight international observers they captured over a month ago, in an apparent goodwill gesture that could help pave the way to a resolution of the conflict that has so far claimed hundreds of lives.

Pro-Russia separatists held eight observers from the Vienna-based Organization for Security and Co-operation in Europe, a security and rights body tasked with monitoring an agreement drafted in Switzerland in April to de-escalate the crisis.

Four observers from Switzerland, Turkey, Estonia and Denmark, part of the 100-strong mission, were brought by heavily armed rebels to a hotel in downtown Donetsk, where they were handed over to their colleagues. Another four remain in captivity in the neighboring Luhansk region.