Russian President Vladimir Putin has evoked the Battle of Stalingrad to predict victory over what he called “the new Nazism” in Ukraine. The remarks came during a commemoration of the 77th anniversary of the battle, which saw Soviet forces break the German siege of the city in 1943.

At the event, Putin also warned of a “new threat” posed by German tanks, and unveiled a series of new busts of Soviet leader Joseph Stalin.

The comments come amid a period of heightened tensions between Russia and Ukraine, which have been embroiled in a conflict since 2014. Russia has been accused of providing military support to pro-Russian separatists in eastern Ukraine, and has been subject to a number of sanctions from the West.

In response to Putin’s remarks, Ukrainian President Volodymyr Zelensky said he was “deeply disappointed” by the Russian leader’s “unacceptable” words. He added that the Ukrainian people “will never accept the occupation of our homeland.”

The United States also expressed its concern over the situation, with a spokesperson for the State Department saying that “Russia’s continued aggression in Ukraine is unacceptable and runs counter to international law.”

The conflict in Ukraine has claimed the lives of more than 13,000 people since 2014, and shows no signs of abating.