A Russian attack killed at least 49 people, including a six-year-old boy, as they gathered in a cafe for a memorial service in a village in northeastern Ukraine on Thursday, the country's interior minister said.

A cafe and a shop were struck early in the afternoon in the village of Hroza in the Kharkiv region, regional governor Oleh Synehubov said, adding that many civilians had been there at the time.

Interior Minister Ihor Klymenko said that residents of the small village of about 330 people had been holding a memorial service in the cafe that was hit.

"From every family, from every household, there were people present at this commemoration. This is a terrible tragedy," Klymenko told Ukrainian television.

Seven people were also in hospital after the attack, which appeared to be the most devastating Russian strike on a residential area in weeks.

Officials posted footage of rescue workers clambering through smoldering rubble. Some photos showed bodies lying alongside slabs of concrete and twisted metal, and others showed rescue workers carrying away covered bodies.

Klymenko said it was not immediately clear whether Russian forces, who invaded Ukraine 19 months ago, had shelled the village or had fired a missile.

He said the strike was clearly very targeted and that Ukrainian security services had launched an investigation into the matter.

President Volodymyr Zelenskiy, who was attending a summit with European leaders in Spain, said that "the Russian terror should be stopped".

"Now we are talking with European leaders, in particular, about strengthening our air defence, about strengthening our soldiers, about giving our country protection from terror," he said in a post on the Telegram messaging app.

Russia has frequently carried out air strikes since the start of its full-scale invasion in February 2022, and Ukraine has launched a counteroffensive in the south and east that it says is gradually making progress.

Moscow did not immediately comment on the events in Hroza. Moscow denies deliberately targeting civilians, many have been killed in attacks that have hit residential areas as well as energy, defence, port, grain and other facilities.