Arrangements are underway for a team of experts from the International Atomic Energy Agency to visit the Zaporizhzhia nuclear plant in Ukraine, where continued shelling is raising concerns about a severe accident.
The large nuclear plant in southeastern Ukraine has been seized by Russian forces. Ukraine and Russia blamed each other for the attacks on Saturday.
IAEA Director General Rafael Mariano Grossi hopes to lead the team to visit the plant as early as this week.
Ukraine's state nuclear power company, Energoatom, says staff at the plant are under increased pressure from Russian forces not to speak out about the military buildup.
Russia's state-run Tass news agency reported that Russian troops detained two Zaporizhzhia employees for allegedly handing over information to the Ukrainian side.
The agency also said 26 employees have been detained since Russia took control of the plant in March.
The Russian military is believed to be turning the plant into a base. All eyes are on whether the planned IAEA visit will help ensure the safety of the plant.
Russia's defense ministry said on Saturday that its troops had killed more than 200 Ukrainian soldiers in the eastern region of Kharkiv.
The ministry also said a missile strike destroyed a depot of the US-supplied HIMARS rocket systems in the eastern Dnipropetrovsk region.
The human casualties on the Russian side are believed to be huge.
President Vladimir Putin issued a decree last Thursday to increase the total number of soldiers in the country's military by more than 130,000 to 1.15 million.
But the British defense ministry said on Sunday that it remains unclear how "Russia will attempt to fill this increased allocation."
The ministry also said "the decree is unlikely to make substantive progress towards increasing Russia's combat power in Ukraine."