The blast in a small community near the central Ukrainian city of Dnipro injured 20 residents, including five children.

“Unfortunately, there are people under the rubble,” President Volodymyr Zelenskiy wrote via messaging app Telegram.

“Once again, Russia proves it is a terrorist state.”

Regional governor Serhiy Lysak said three of the children suffered serious injuries. A total of 17 people were receiving medical attention.

Media reports said emergency teams had pulled four people from under rubble in the town of Pidhorodnenska.

Lysak said another child was likely still trapped.

Reports on social media said a Russian missile caused the explosion and that an emergency services building was also hit.

Moscow has not commented on the incident but routinely denies its forces target noncombatants and civilians.

Pictures posted on social media showed rescue teams working at a shattered, smouldering building amid piles of twisted building materials.

Offensive ready to roll

Separately, Zelenskiy believes Ukraine is ready for a long-awaited counter offensive to liberate its territories from Russian occupation, while in Russia, there was criticism of Moscow’s efforts in the war.

“In my opinion, as of today, we are ready to do it,” he said in an interview with the Wall Street Journal, which the US newspaper also published as a video on its website on Saturday.

Zelensky also said Ukraine would have liked to have some more weapons for the offensive against the Russian invasion, but could not wait months more for their delivery.

“We strongly believe we will succeed,” he said, according to the WSJ‘s translation. “I don’t know how long it will take.”

He said the price for success would be high.

For months there has been speculation about the start of the offensive; at times it was said in Kyiv that the operation was already underway.

Bitterly divided Russian forces

Meanwhile the head of the Russian private army Wagner, Yevgeny Prigozhin, accused the Russian Defence Ministry of failing.

“The ministry is not able to do anything. There is chaos in the ministry,” he said, also referring to the faltering war on Ukraine.

Prigozhin is a close confidant of Russian President Vladimir Putin. He said he himself would march to the region with his troops if the Russian military does not establish order there “as quickly as possible”.

“There is already a conquest of the area going on there. Peaceful people are dying,” Prigozhin said.

“The population needs protection. We will not wait for an invitation.”

However, he said, the Russian military must provide ammunition. “Otherwise, as they say, we will be sitting on our bare asses on the frost.”

Prigozhin defended his criticism of the Russian Defence Ministry and parts of the Kremlin in a lengthy speech on Telegram. He has recently faced threats from Chechen leader Ramzan Kadyrov’s army. Prigozhin has also been asked to refrain from his public attacks on the ministry.

He has since cleared up the dispute through a phone call with Kadyrov, Prigozhin said, though adding that he refused to be muzzled.

Kremlin’s recruiting drive

Prigozhin said again that he agreed with Kadyrov that it would take a general mobilisation and martial law to win the war – steps that the Kremlin has so far refused to take.

However, Russia’s Defence Ministry said it had expanded the number of mustering points to recruit volunteers for the war.

There are more such points and more instructors to work with candidates, the ministry said. This would allow more contracts to be signed with citizens to serve in the war.

The number of applicants who “want to combine their lives with military service” has increased to a “significant extent,” the ministry said.

These efforts are now being organised more effectively in the Moscow region and in the Bashkir region, it said.

The Wagner Group are also recruiting volunteers, offering salaries the equivalent of more than $US2000 ($A3025), which is much more than people in Russia earn on average.

-with AAP