A baby aged just 23 days, her 12-year-old brother and their parents were among seven people killed by Russian shells in southern Ukraine on Sunday.

Bombs hit their family home in the village of Shyroka Balka in Kherson, Interior Minister Igor Klymenko said.

The dead also included another village resident and two men in the neighbouring Stanislav.

"Terrorists must be stopped. They must be stopped by force," said Mr Klymenko. "They don't understand anything else."

The minister shared photographs of the aftermath of the attack on Shyroka Balka, showing black columns of smoke rising from buildings, and the digitally obscured bodies of some of the dead.

Kherson was one of four regions in Ukraine that Russian President Vladimir Putin claimed to have annexed last year.

Ukraine's military reclaimed the western part of the region last November but Russian troops have continued to shell the area from across the Dnipro river.

The shelling came a day after Russia accused Ukraine of "terrorism" for what it said was an attempted missile strike on the Kerch Bridge linking mainland Russia with the Crimean peninsula.

Ukraine has not confirmed the attack, although President Volodymr Zelensky has said the bridge is used as a military supply route and is a legitimate target.

In another development, Moscow said it had fired warning shots at a cargo ship in the southwestern Black Sea as it made its way to the Ukrainian port of Izmail.

It is the first time Russia has fired on merchant shipping beyond Ukraine since exiting a landmark UN-brokered grain deal last month.

Russia said in a statement that its Vasily Bykov patrol ship had fired automatic weapons on the Palau-flagged Sukru Okan vessel after the ship's captain failed to respond to a request to halt for an inspection.

"After the inspection group completed its work on board, the Sukru Okan continued on its way to the port of Izmail," the defence ministry said.

Meanwhile, an aide to the exiled Ukrainian mayor of Mariupol reported that several Ukrainian civilians were killed as Russian soldiers fought among themselves on Sunday.

Two teenage girls, four young men and a woman were among the dead in the "shoot-out" in the village of Urzuf, Petro Andryshchenko said in a Telegram post.

He said the gun battle followed an argument between Chechen soldiers and personnel from the local commandant's office.