Ukrainian President Volodymyr Zelensky called for Russia to be investigated for war crimes on Tuesday. 

His call comes after an attack on Ukraine’s second-largest city, Kharkiv, that killed at least 10 people and wounded 35 others.

“This is the price of freedom,” Zelensky said, the BBC reported. “This is terror against Ukraine. There were no military targets in the square – nor are they in those residential districts of Kharkiv which come under rocket artillery fire.”

He continued to say the shelling was “frank, undisguised terror.”

“Nobody will forgive. Nobody will forget. … This is state terrorism of the Russian Federation,” The Associated Press reported.

Along with the attack on Kharkiv, Russia has reportedly used cluster bombs against Ukraine, which are banned under an international treaty. 

Russia has denied targeting civilians or committing war crimes during its invasion of Ukraine, the AP noted. 

European Parliament members gave Zelensky a standing ovation on Tuesday after he pleaded for help during remarks from Kyiv.

U.S. intelligence reportedly says Ukrainian resistance to the invasion has been stronger than expected, as Russia has still not taken over the capital city of Kyiv.