Residential areas in Kharkiv, Ukraine’s second-largest city, were being pounded by Russian shells while satellite imagery showed a massive 40-mile convoy of Russian tanks and vehicles rolling toward the Ukrainian capital of Kyiv on Tuesday as the Ukraine war roared into its sixth day.

Ukrainian President Volodymyr Zelenskyy called an attack on Kharkiv’s main square “frank, undisguised terror” and a war crime.

“Nobody will forgive. Nobody will forget,” Zelenskyy said. “This is state terrorism of the Russian Federation.”

Lengthy talks Monday aimed at stopping the war yielded only an agreement to keep talking. Zelenskyy said stepped-up shelling was aimed at forcing him into concessions.

Kharkiv Mayor Ihor Terekhov said Tuesday that his government remained under control but said the city is surrounded by Russian troops.

“Military equipment and armored vehicles are coming from different directions,” he told The Washington Post in a phone interview.

Terekhov said a government building and the opera and ballet theater were among building shelled. Transformer stations were also struck by artillery, cutting off power to much of the city, he said. The shelling had stalled efforts to supply the city with food and medical supplies, he said.

“There are casualties, and by now, there are certainly a lot more of them, after the night and morning shelling,” he told the Post. “The situation is pretty grave.”