The coordinator of the working subgroup of the Trilateral Contact Group on Ukraine has expressed concern over a sharp increase in the number of ceasefire violations in Donbas, said Martin Sajdik, a Special Representative of the Organization for Security and Co-operation in Europe (OSCE).

There has been a sharp rise in ceasefire violations, especially after April 6, up to 4,700 violations in one day alone, Sajdik told reporters in Minsk on Wednesday.

Heavy weapons were seen being used during hostilities, he said.

Combatants used heavy weapons, artillery and mortar launchers which had been previously removed from the contact line, the OSCE special representative said.