Petro Symonenko, leader of the Ukrainian Communist Party, has called on the parliament to immediately discuss the issue of changing the country's state system.

"I suggest making an immediate decision on changes to the Constitution and making an immediate decision on the federalization of Ukraine to maintain the integrity of Ukraine and keep the Luhansk and Donetsk regions parts of Ukraine," Symonenko told a meeting of the Ukrainian parliament's conciliatory council on Monday.

Symonenko also demanded that the Ukrainian authorities immediately stop the military operation because Ukraine may lose another two regions. He also called for investigations into crimes against civilians.

"We have already drawn up several suits to international courts and we will submit them to the parliament for consideration, this document, and we'll see how you will react," Symonenko said.