Ukrainian President Volodymyr Zelenskyy has repeated his determination to continue counteroffensives to liberate more areas occupied by Russia's military.
Zelenskyy released a video on Sunday, after the Ukrainian military announced that it had freed almost all of the eastern region of Kharkiv from Russian forces.
The president said, "Perhaps it seems to someone now that after a series of victories we have a certain lull. But this is not a lull. This is preparation for the next sequence."
He expressed his willingness to continue counteroffensives to liberate other Russian-occupied areas, such as Kherson in the south and Mariupol in the east.
Meanwhile, Ukrainian authorities are investigating a mass burial site found in the city of Izyum in Kharkiv.
On Sunday, the city's mayor said on a TV program that completion of the entire work is expected to take about two weeks.
Reuters news agency says what is believed to be a torture cellar used by Russian forces was found near Derhachi, also in Kharkiv.
A video shows a dirty mattress, blankets and scattered dishes in a room behind bars. It also shows damage caused by a shell.
The Derhachi mayor said Russian soldiers kept local civilians in the cellar without food or medical supervision after beating them for the purpose of obtaining information.