KIEV: President Volodymyr Zelensky on Tuesday invited Russian leader Vladimir Putin to meet in war-torn eastern Ukraine, stressing that millions of lives were at stake from fresh fighting the separatist conflict.

The blunt offer for talks came following a flare-up in clashes between Ukraine's army and pro-Russian separatists controlling two regions in the country's east, raising concerns of a major escalation in the simmering war.

In an address to the nation, Zelensky said that Ukrainian and Russian negotiators had recently discussed plans for officials to travel to the frontlines of the trench conflict to assess the situation.

"I am ready to go even further and invite you to meet in any part of the Ukrainian Donbass where war is ongoing," Zelensky said.

The Ukrainian president, elected in 2019 on promises to bring an end the conflict, accused Russia of participating in peace negotiations while massing troops on Ukraine's border.

"A considerable number of Russian troops are concentrated near our border," he said. "Officially, Russia calls this military exercises. Unofficially, the whole world calls this blackmail.

"The Russian president once said that if a fight is inevitable, you need to hit first. But every leader needs to understand that a fight must not be inevitable when it concerns a real war and millions of human lives."

Ukraine, the European Union and the United States have recently sounded the alarm over renewed tensions and accused Russia of massing tens of thousands of military personnel on the northern and eastern borders of the ex-Soviet country.

The EU on Monday estimated the number of Russian troops along the Ukrainian border at more than 100,000 during talks with Ukraine's foreign minister, who encouraged Western countries to hit Russia with a deeper package of economic sanctions over the conflict.