STORY: Kharkiv, Ukraine's second biggest city, had been relatively quiet since Ukrainian forces regained territory around it and pushed back Russian troops this month, enabling the authorities to reopen the city metro network.
But Russia appears to have halted its retreat and a Reuters correspondent in Kharkiv said repeated explosions could be heard on Thursday as Russian forces dug in and maintained control of positions in villages north of the city.
Russia didn't immediately comment on the situation in Kharkiv. It has denied targeting civilians in what it calls a "special military operation" launched on Feb. 24.
When Kharkiv resumed its metro service on Tuesday (May 24), it asked the hundreds of people who had used the underground as a bomb shelter to free up the train carriages, but many said they were still too scared to return home.