After the fall of the strategic town of Debaltseve in eastern Ukraine, Ukrainian President Petro Poroshenko proposed that international peacekeepers oversee the cease-fire in the war-torn east of the country. However, Kiev's call on the U.N. and EU to deploy a peacekeeping mission was heavily criticized by Russia and pro-Russian separatists groups, as the idea of a U.N. and EU presence in Ukrainian territory severely disturbed the rebels and Russia. Russia's aggressive stance toward Ukraine's proposal for the U.N. is highly controversial. Russia's aggressive stance toward Ukraine's proposal for the U.N. is highly controversial as Russia continues to intervene militarily, not only in Ukraine and Crimea, but in other ex-Soviet countries like Moldova and Georgia, claiming to protect fellow Russians, and overtly extending its sphere of influence. With no sign of easing tensions, Moscow wants to maintain influence in rebel-held areas in eastern Ukraine. A potential U.N. presence would damage Russia's interest in the region.Amid growing security concerns, the Ukrainian Security and Defense Council announced its approval of Poroshenko's request in an emergency meeting on Wednesday. "The best format for us is a police mission from the EU," Poroshenko said in a statement released on his website. "It will be the most efficient guarantor of security in the situation when the word peace is not observed either by Russia or by those who are supported by it."Russia denounced the call for U.N.-mandated peacekeeper while accusing Ukraine of aiming to violate the Minsk Accords. Russia's U.N. ambassador, Vitaly Churkin, accused Poroshenko of not following the rules proposed in the Minsk Agreement. "If one proposes new schemes right away, the question arises whether [the Minsk Accords] will be respected," he said. Pro-Russian rebel groups said Poroshenko's call for U.N. peacekeepers to observe the volatile cease-fire in the eastern Ukraine would be "an actual violation of the package of measures to implement the Minsk Agreement."Ukraine's call to the U.N. came after pro-Russian rebels seized the strategic eastern town of Debaltseve after the cease-fire took effect on Sunday. Hundreds of Ukrainian troops have begun to pull out of the town that has been under siege by pro-Russian rebel forces since January. Debaltseve, which serves as a strategic transport hub in the northeast of the separatist stronghold of Donetsk, has seen heavy shelling between Ukrainian forces and rebel groups. A total of 2,475 Ukrainian military personal and almost 200 vehicles and pieces of army hardware had been withdrawn from Debaltseve, Poroshenko said at a meeting of the National Security and Defense Council on Wednesday, according to the Russian state-run Itar-Tass news agency. "We have completed an operation on clearing Debaltsevo," the head of the self-proclaimed Donetsk People's Republic, Alexander Zakharchenko, said on Thursday. "Unfortunately, Ukrainian authorities have failed to listen to reason and lay down their arms," he added.The cease-fire agreement negotiated in four-power talks on February 12 includes the withdrawal of all foreign weapons and troops from Ukrainian territory and the disarmament of Russia-backed rebel groups. The shaky truce is generally holding in violence-stricken eastern Ukraine. However, the breaches of the Minsk Accords have been widely reported, signaling that the months-long crisis in Ukraine's east has yet to be resolved despite a series of mediating talks and peace efforts.Meanwhile, in the wake of the proposal for a U.N. peacekeeping mission to help implement the shaky cease-fire between Ukrainian troops battling the advance of pro-Russian rebels in the east of the country, the U.K. warned of a Russian expansionist threat in Baltic countries. Britain's defense minister, Michael Fallon, voiced concern over Russia's aggression in European territories, considering the security situation in Baltic countries – Estonia, Latvia and Lithuania – saying that Russia poses "a real and present danger," as reported by Reuters. "I'm worried about [Russian President Vladimir Putin's] pressure on the Baltics, the way he is testing NATO. NATO has to be ready for any kind of aggression from Russia, whatever form it takes. NATO is getting ready," he said.After the annexation of Ukraine's Crimean peninsula by Russia in March, there has been a growing fear among northern European states that the Cold War years could be making a return. Regarding Russia's aggressive actions in several break-away regions, Russia's increased militarization of rebel-held areas in the Donbass region and its explicit support for pro-Russian separatists who are seeking regional leadership close to Russia, have prompted fears among ex-Soviet states that are now committed to a pro-Western path.International law that underpins the principle of maintaining territorial integrity has been challenged by Russian military intervention in Ukraine. During violent fighting in the region, reports indicate that many Russian troops, military vehicles and humanitarian convoys have crossed into Ukraine without the Ukrainian government's permission. Russian troops have allegedly fought alongside rebels against Ukrainian troops. Ukraine and Western countries have accused Russia of backing and financing rebel militias, but Russian authorities have denied all charges. Western countries have accused Russia of violating the cease-fire agreement, noting that Russia would face additional sanctions if it continues to provide support to rebels in eastern Ukraine. The unwillingness of Putin's Russia to implement the Minsk Protocols by backing separatist groups has long been criticized by the administration of U.S. President Barack Obama. Since clashes erupted in eastern Ukraine, more than 2 million Ukrainians have been forcibly displaced due to worsening humanitarian conditions in rebel-held areas where heavy fighting has turned eastern Ukraine into a battle zone. According to U.N. figures, more than 5,600 people have been killed during heavy clashes between armed groups since the hostilities erupted in late March.