More than 70 Ukrainian soldiers were killed after Russian artillery hit a military base in Okhtyrka, a city between Kharkiv and Kyiv, the head of the region wrote on Telegram.

Dmytro Zhyvytskyy posted photographs of the charred shell of a four-story building and rescuers searching rubble. In a later Facebook post, he said many Russian soldiers and some local residents also were killed during the fighting on Sunday. The report could not immediately be confirmed.

“I believe Russia is trying to put pressure (on Ukraine) with this simple method,” Ukrainian President Volodymyr Zelenskyy said late Monday in a video address. He did not offer details of the hours-long talks that took place earlier, but said that Kyiv was not prepared to make concessions “when one side is hitting each other with rocket artillery.”

Earlier Monday, Russian forces shelled Ukraine’s second-largest city, rocking a residential neighborhood as they closed in on the capital, Kyiv, in a 40-mile convoy that included hundreds of tanks and other military vehicles.

The fighting continued as talks aimed at stopping the war yielded only an agreement to keep talking. The country’s embattled president said the stepped-up shelling was aimed at forcing him into concessions.

As Russian forces marched forward and met stiff resistance from Ukrainian soldiers, countries tightened the vise around Moscow’s economy Monday, announcing new sanctions on its central bank and individuals. Even Switzerland is breaking its neutral stance to join the EU in its actions.