In Moscow, a senior Kremlin official sternly warned Ukraine against the use of force to regain control of rebels in the east, saying it could force Russia to intervene to protect civilians there.
Conflict with Russian-backed separatists in eastern Ukraine erupted shortly after Moscow’s annexation of Ukraine’s Crimean peninsula in 2014. More than 14,000 people have died in the fighting.
Analysis: Russia uses Putin’s old tactics to justify military presence near Ukraine border
Ukrainian and Western officials have expressed concern over the growing ceasefire violations in the country’s industrial center, known as Donbass.
They also accused Russia of sending troops and weapons along the border to support the rebels there – accusations the Kremlin has denied.
And after tweeting that he wanted “to be with our soldiers in the difficult times of Donbass,” Ukrainian President Volodymyr Zelenskiy arrived in the heart of the conflict zone on Thursday.
He said a 23-year-old Ukrainian soldier was killed in the area on Wednesday evening.
He told the troops, “Thank you for keeping the people calm and defending our land. You are a true example of heroism and dedication. We remember every warrior who died defending our state. “
Zelenskiy accused Russia of showing military force and organized a series of appeals with Western leaders to rally support for Ukraine amid the tensions.
Russia rejected these claims, arguing that it could deploy its troops wherever it deemed necessary on its territory and that it was not threatening anyone.
He accused the Ukrainian authorities of trying to rekindle tensions in the east for domestic political purposes.
The White House is said to be “increasingly concerned about the recent escalation of Russian aggressions in eastern Ukraine”, including Russian troop movements on the Ukrainian border.
Press Secretary Jen Psaki said: “Russia now has more troops on the border with Ukraine than at any time since 2014.
“Five Ukrainian soldiers have been killed this week alone. These are all signs of deep concern. “
Speaking at a roundtable with political experts in Moscow, Dmitry Kozak, a Putin aide who is Russia’s main negotiator with Kiev, warned Ukraine against using military force to resume control of the eastern regions, where many residents obtained Russian citizenship.
“The start of hostilities will mark the beginning of an end for Ukraine,” he said. “It would mean shooting yourself not only in the foot, but in the head. ”