(AGI) Rome, June 4 - Tensions are rising once again in easternUkraine after clashes between Kiev's troops and pro-Russianrebels left 26 dead over the last 24 hours, namely in theMaryinka area west of Donetsk. "There remains a colossal threatof resumption of large-scale fighting on the part of Russianterrorist groups," Ukrainian President Petro Poroshenko statedon Thursday. "The military must be ready as much for a renewalof an offensive by the enemy in the Donbass as they are for afull-scale invasion along the whole length of the border withRussia. We must be truly ready for this," he warned. Poroshenkosaid over 9,000 Russian soldiers are already on Ukrainian soil.The UN Security Council will hold an emergency meeting onFriday after a request by Lithuania. Fourteen rebels and fivecivilians have been killed in eastern Ukraine in the last day,with 24 civilians and 86 rebels injured, according to aUkrainian separatist leader, Eduard Basurin. Kiev reported thatfive of its soldiers were killed and 39 wounded. The fightingin Maryinka ended after Wednesday's battle, but the EU isalarmed by the warlike actions. "The heavy fighting aroundMariyinka, near Donetsk, yesterday in Eastern Ukraineconstitutes the most serious violation of the ceasefire underthe Minsk agreements since February," said the EU Commission'sspokesperson, Maja Kocijanic. "This escalation followed themovement of a large amount of heavy weapons towards the contactline by the Russia-backed separatists, as reported by the OSCESpecial Monitoring Mission." The U.S. also expressed concernand warned that there would be consequences for Moscow shouldthe fighting escalate. NATO chief Jens Stoltenberg urged bothsides to fully apply the Minsk agreement, starting withremoving their heavy artillery. Russia, meanwhile, accusedUkraine of seeking provocation before the G7 summit in Germanythis weekend and the European Council on June 25, which willdecide whether to renew sanctions on Moscow. Kiev's parliamentapproved a law on Thursday authorising the deployment offoreign troops on its territory to maintain peace and security,on the condition of a UN or EU mandate and excluding countriesinvolved in a "military aggression" against Ukraine.. .