Russian strikes on Ukraine's southern Kherson region killed 21 people and wounded dozens on Wednesday, Kyiv said, as authorities introduced a curfew in the main city of Kherson starting Friday.

The strikes -- which hit both the city and nearby villages -- came as Ukraine prepares for a spring offensive. President Volodymyr Zelensky said the strikes hit "a railway station and a crossing, a house, a hardware store, a grocery supermarket and a gas station."

Kherson city -- from which Russian forces withdrew last November -- lies near the frontline in southern Ukraine. "As of now, 21 people have been killed! 48 wounded!", Zelensky said on Telegram.

He published images of bodies and wounded people on the floor of a vegetable aisle at a supermarket, with debris around them. "The world needs to see and know this," Zelensky said.

Kherson prosecutors had called the attack "massive", noting 12 of the victims were killed in the city and others in nearby villages. "On the morning of May 3, Russian troops began the massive shelling of the city of Kherson and the region's settlements," the prosecutors said.

Officials had earlier said three people died in a strike on Kherson's only working hypermarket. The prosecutors said shelling killed three employees of a "power engineering team" between the nearby villages of Stepanivka and Muzykivka.

Officials also announced Wednesday that Kherson will be under curfew from Friday to Monday. Long curfews have been used in  Ukraine in the past to facilitate troop and arms movements.

The head of Kherson's regional military administration Oleksandr Prokudin said the curfew would last from 1700 GMT on Friday until 0300 GMT on Monday. "During these 58 hours, it is forbidden to move on the streets of the city. The city will also be closed for entry and exit," Prokudin said on Telegram, advising residents to stock up on food and medicine.

People could go for short walks near their houses or visit shops but should carry identity documents with them. "Such temporary restrictions are necessary for the law enforcement officers to do their job and not put you in danger," he wrote. Kherson was captured by Russian troops last year in the first days of the invasion and remained under Russian occupation until November 2022. Russian forces withdrew from the city, crossing to the eastern side of the Dnipro River which now delineates part of the front line in southern Ukraine.