Ukrainian Army combat engineers prepare foucade bombs for the destruction at Donbas (Donetsk region), Ukraine, on June 11, 2014. (XINHUA/SIPA)

KIEV, April 5 (Xinhua) -- Ukraine will end its "anti-terror" operation (ATO) against pro-independence rebels in the eastern region of Donbas in May, Ukrainian President Petro Poroshenko announced on Thursday.

"We are moving to another format of the country's defense," Poroshenko was quoted as saying by his press service.

The format of the military operation will be changed in accordance with the law on Donbas re-integration, Poroshenko said.

"We are introducing completely new, more effective measures for the use of the Armed Forces with the expansion of our defense capabilities," he said.

The controversial law on Donbas re-integration, which defines areas controlled by rebels in eastern Ukraine as "temporarily occupied territories," came into the force on Feb. 24.

The Russian Foreign Ministry has warned that the legislation could lead to an escalation of the confrontation in Donbas.

The conflict in Donbas region started in April 2014, after government forces launched offensives to regain control of the cities and towns seized by armed groups which declared independence from Kiev.