OSCE Chairperson-in-Office Dacic appeals for boost to political process in eastern Ukraine/ Photo from osce.org

He also expressed in particular serious concern over the use of proscribed heavy weapons as well as the increased fighting in and around Donetsk and Shyrokyne, the OSCE press service reported.

He once again reiterated the call, supported in Belgrade last week by the ministerial OSCE Troika, to all sides to fully and unconditionally respect the ceasefire, end all hostilities and implement all provisions from the Minsk Agreements, including the withdrawal of heavy weapons.

"At this moment, it is essential for the political process to gain momentum, and I call all sides to invest all possible efforts towards that end," the press service quoted Dacic as saying.

He also reiterated his full support for the activities of the Special Monitoring Mission to Ukraine (SMM) in Donbas