Nikopol, on the the opposite bank of the Dnieper River and about 10 kilometers (6 miles) downstream from the plant, came under fire three times during the night from rockets and mortars, hitting houses, a kindergarten, the bus station and stores, regional governor Valentyn Reznichenko said. There was no information on injuries or loss of life.

Reports of sustained shelling around Europe's largest nuclear power plant further highlighted the dangers of a war that will hit the half-year mark on Wednesday.

After U.N. Secretary General Antonio Guterres again urged caution during a visit to Ukraine last week, U.S. President Joe Biden further discussed the issue with the leaders of France, Germany and Britain on Sunday.

The four leaders stressed the need to avoid military operations in the region to prevent the possibility of a potentially devastating nuclear accident and called for the U.N.'s atomic energy agency to be allowed to visit the facilities as soon as possible.

Yet, nothing seemed certain in a war that has spread fear and unease far beyond the frontlines in eastern and southern Ukraine and also into the Russia-annexed Crimea peninsula and as far as Moscow, where on Saturday night a car blast killed the daughter of an influential Russian political theorist often referred to as ``Putin's brain.''

On Monday Russian authorities were looking for further clues who could be behind the incident, after authorities said preliminary information indicated 29-year-old TV commentator Daria Dugina was killed by an explosive planted in the SUV she was driving.

A former Russian opposition lawmaker, Ilya Ponomarev, said an unknown Russian group, the National Republican Army, claimed responsibility for the bombing. The AP could not verify the existence of the group. Ponomarev, who left Russia after voting against its annexation of Crimea in 2014, made the statement to Ukrainian TV.

Ukraine officials have denied involvement.