Service members of the Ukrainian armed forces stand guard at combat positions near the line of separation from Russian-backed rebels in the town of New York in the Donetsk region, Ukraine, February 9, 2022.Oleksandr Klymenko | ReutersUkraine has claimed pro-Russian separatists in the country’s east opened fire on civilian territory on Thursday, damaging a kindergarten.”The shelling of a kindergarten in Stanytsia Luhanska by pro-Russian forces is a big provocation,” Ukrainian President Volodymyr Zelenskyy said Thursday on Twitter. “It’s important that diplomats and the OSCE [Organization for Security and Cooperation in Europe] remain in Ukraine, [as] their monitoring activities are an additional deterrent.”Ukraine’s Ministry of Defence later said that shelling had stopped as of 1 p.m. local time, according to Reuters.Earlier Thursday, the Ukrainian Joint Forces Operation said on Facebook that pro-Russian separatists had shelled 22 settlements in the Donbas region of eastern Ukraine, with civilians and military personnel sustaining injuries.”A total of 32 shells were fired by terrorists,” the statement said. “The shelling damaged kindergartens and communal infrastructure — half of the village was left without electricity.”Three of the kindergarten’s employees were injured, the JFO added, and children and caregivers had been evacuated.Separately, the Ukrainian Defence Ministry reported that a school building with pupils and teachers inside was damaged by shelling on Thursday. No one was reported to be hurt in the attack. A view from the shelled kindergarten in eastern Ukraine on February 17, 2022.Ukrainian Chief of General Staff | Anadolu Agency | Getty ImagesIt also alleged that Russian mercenaries had opened fire in several other locations in eastern Ukraine using artillery and grenades, with the country’s Ministry of Defense claiming Russian occupation forces had committed 29 cease-fire violations by 11 a.m. local time.”Ukrainian defenders opened fire in order to stop the enemy’s fire activity,” the JFO said in its statement.It released photos and video footage of the kindergarten it said had been hit by ammunition. CNBC has been unable to verify the reports.’Crucial moment’U.S. Secretary of State Antony Blinken announced a last-minute change of travel plans on Thursday following the reports of violence, and will speak at a U.N. Security Council meeting on Ukraine before traveling to Munich, Germany.”The evidence on the ground is that Russia is moving toward an imminent invasion,” U.S. Ambassador to the U.N., Linda Thomas-Greenfield, said in a statement on Thursday. “This is a crucial moment.”Kyiv’s accusations come after Russian-controlled media agency RIA claimed earlier Thursday that Ukrainian forces had shelled territory held by pro-Moscow separatists. Kyiv quickly denied the reports, which CNBC has been unable to verify.The east of Ukraine, near the Russian border, has long been the scene of low-level fighting. The OSCE has regularly reported violations of the ceasefire in eastern Ukraine during the eight-year conflict, in which around 13,000 people have died.’False claims’ could precede invasion, U.S. warnsReports of heightened violence on Thursday follow warnings from the U.S. that Moscow could use false claims about the conflict as a pretext for an invasion of Ukraine.”Over the past few weeks, we’ve seen Russian officials and Russian media plant numerous stories in the press, any one of which could be elevated to serve as a pretext for an invasion,” State Department spokesperson Ned Price said in a statement on Wednesday.He also reiterated that Russia’s claims about a partial pullback of its troops from the border had not been verified by the United States.”We are doing everything we possibly can to find a peaceful resolution to the crisis the Kremlin has needlessly precipitated. But those efforts will be effective only if the Russian Federation is willing to deescalate,” he said. “To be very, very clear, we have not seen that. In fact, we have seen the opposite. In recent weeks, and even in recent days, more Russian forces — not fewer — are at the border, and they are moving, concerningly, into fighting positions.”A senior Biden administration official told reporters Wednesday night that as many as 7,000 troops have joined those already near the border in recent days, after Western officials accused Moscow of sending “mixed signals” over its position on Ukraine.Russia has amassed more than 100,000 soldiers, tanks, missiles and even fresh blood supplies at the Ukrainian border, but has repeatedly denied it is planning to invade Ukraine.The Kremlin released video footage on Wednesday which it claimed showed military units returning to their permanent deployments after completing exercises near the border, however multiple Western officials have said that Russia’s troop count at the border is in fact increasing, not decreasing.Security guaranteesRussia has requested several security guarantees from the U.S. and NATO — the world’s most powerful military alliance — over recent weeks, including demands that Ukraine never be permitted to become a member of the organization and that NATO presence in Eastern Europe is scaled back.Last month, the U.S. delivered a response to Russia’s proposals, repeating previous refusals of those demands. Russian Foreign Minister Sergey Lavrov told a press conference on Thursday that Moscow will respond to the U.S. response today, according to state media.Russia’s Duma (parliament) voted on Tuesday to ask President Vladimir Putin to recognize two Moscow-backed breakaway regions, Donetsk and Luhansk, in eastern Ukraine as independent republics.Both Ukraine’s government and U.S. Secretary of State Antony Blinken said on Wednesday that such a move would effectively amount to a Russian withdrawal from the Minsk Agreements.The Minsk Agreements — designed to end a separatist war in eastern Ukraine — were signed by representatives for Russia, Ukraine, the Organisation for Security and Cooperation in Europe (OSCE) and pro-Russian separatists in 2014 and 2015.Correction: Early reports of shelling in eastern Ukraine Thursday were not independently verified by CNBC, contrary to an earlier version of this story.