Ukrainian President Petro Poroshenko has expressed concern about militants' pledge to withdraw unilaterally from the Minsk agreements.

"We are concerned about the terrorists' announced withdrawal from the internationally recognized Minsk agreements and their position on the implementation of the peace plan, de-escalation of the conflict, border closure, the rerelease of illegally held persons, heavy weaponry pullout and ceasefire," Poroshenko told the National Security and Defense Council in Kyiv on Sunday.

"Just a few hours before the horrible tragedy in Mariupol, terrorist groups leaders officially announced the beginning of an offensive on the city. This is how they understand what an offensive is," the Ukrainian president said.

However, the rebuff offered by the Ukrainian Armed Forces provides evidence that, "Ukraine is securely protected," Poroshenko said