"[The Secretary-General] hopes that this humanitarian act could serve as a positive step towards strengthening the confidence among the sides," read a statement attributable to his spokesperson Thursday, reads the report.

"[He also] urges all parties to take further measures in this spirit, including by fully respecting and upholding the ceasefire agreement and continuing to work together to fulfill all of their commitments under the Minsk agreements," it added.

Read alsoU.S. calls for "all-for-all" detainee swap in DonbasOn 27 December, more than 300 detainees were released with the participation of the UN partner, International Committee of the Red Cross (ICRC). The operation took place near the town of Maiorsk and is the largest since the beginning of the conflict.

According to the ICRC, this is the first time in 2017 that, at the request of the parties concerned, the ICRC has participated in the release and transfer of detainees held in relation to the conflict in Ukraine.

In late February 2014, the situation in Ukraine transcended what was initially seen as an internal Ukrainian political crisis into violent clashes in parts of the country, later reaching full-scale conflict in the east. Nevertheless, despite a September 2014 ceasefire agreed in Minsk, the situation deteriorated and the crisis is now slipping into its fourth year.