Former Ukrainian President Petro Poroshenko on Sunday asserted that Russian President Vladimir Putin is a "war criminal" for the "disastrous humanitarian situation" inflicted on the Ukrainian people, arguing the now 11-day conflict should be considered "a common war" as the risk to global security rises each day.  

Speaking from the ground in Kyiv, Poroshenko, who served as president of Ukraine from 2014 to 2019, described to FOX Business' "Sunday Morning Futures" the "disastrous humanitarian situation" in several Ukrainian cities, as dozens were killed overnight despite efforts to evacuate civilians.  

"We definitely proud to be the brave Ukrainian soldiers of the unity of Ukrainian people who demonstrate in and ruined all this scenario of Putin," Poroshenko said. "First, he wanted captured Ukraine for 48 hours, then in 72 hours. But today's 11th day of our fighting."

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"Putin is not just an aggressor. Putin is a war criminal. Putin make crimes against humanity," he added. 

Poroshenko noted how the shelling of major Ukrainian cities are happening in the 21st century. 

"This is the genocide against Ukrainian people," Poroshenko said, noting that the Ukrainian people want freedom and hate the idea of the restoration of a "second edition" of the Soviet Union.  

"We should keep Ukrainian airspace above Ukrainian soil," he said. "Definitely, we need the military jet to cover the nuclear power station because nuclear contamination do not see the borders. And Article five of the Washington Treaty do not protect the western world from the disastrous Putin madness." 

Grateful for plans for NATO to send fighter jets from Poland, the Slovak Republic and Germany, Poroshenko said the support was vital because Ukrainian soldiers "protect not only Ukrainian soil, we protect in here the Europe security and global security at the end of the day." 

Russian forces invaded Ukraine’s Donbas region during Poroshenko’s presidency when he was commander in chief of the Ukrainian Armed Forces. He described seeing a change in President Vladimir Putin over the past several years as his ambitions in Ukraine and Europe remain unclear. 

"In 2014 that was another Putin," he said. "Please believe his mental capacity is completely different. And I think that he's a mad person. And I think that the danger for the increasing the dangerous with global security is definitely rising. That's why everybody should understand that this is not just Ukrainian war. This is our common war, and we need to stop Putin. We do not have any other way out."

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Though he prefers a diplomatic resolution to the conflict, he said he was not hopeful for one. 

"I prefer the diplomatic solution. And definitely there is no any nation in the world who wants the peace more than we Ukrainians," he said. "We need to be united. Well, together with the present European Union, for example, France and Germany, and with the participation of United States. This is just to demonstrate the unity and demonstrate the efficiency of the negotiation."