At least 15 people were killed as Russian forces fired rockets at Ukraine's second-largest city Kharkiv and the surrounding countryside in an attempt, according to Kyiv, to persuade it to remove resources from the main battlefield to protect civilians from attack.

A fire ravaged a Russian oil plant five kilometers from the Ukrainian border. The Russian news agency TASS quoted a local official reporting that a drone had hit it.

The Russian attacks on Kharkiv on Tuesday and Wednesday morning were the deadliest in weeks in an area where everyday life had been returning since Ukraine beat back Russian forces last month in a strong counteroffensive.

"They were bombardments by Russian soldiers. Most likely several missile launchers And it's the missile hit, it's all the missile impact," Kharkiv prosecutor Mikhailo Martosh told Reuters amidst the rubble of Tuesday's missile strike in a rural area on the city's outskirts.

The body of an older woman was removed from the ruins of a burned-out garage and loaded into a nearby van by medical personnel.

She had 85 years of age. A child of conflict (World War Two). "She survived a previous war, but not this one," remarked her grandson Mykyta. "There are no escape routes. "Most especially grandmother herself, she did not want to leave."

According to Ukrainian authorities, 15 people were killed, and 16 were injured in shelling in the Kharkiv region on Tuesday, with reports of additional casualties overnight and on Wednesday morning.

Oleksiy Arestovych, an adviser to the Ukrainian president, claimed in a video address that Russian soldiers are frightening the population of Kharkiv in the same way they terrorized the people of Mariupol.

"If they continue to do this, we will be forced to respond, and this is one way to force us to move our artillery," he warned. "The plan is to generate one large difficulty to divert our attention and force us to redirect our forces. I believe that there will be escalation."

The Russians bombarded Kharkiv for the first three months of the war, but the city has been mostly spared since the Ukrainian counteroffensive more than a month ago.

The principal battlefield is now in the Donbas region to the south, which Moscow has been attempting to conquer on behalf of its rebel proxies.

Moscow has made only modest progress while employing overwhelming weaponry in some of the fiercest ground fighting in Europe since World War II, which has taken place in the Donbas.

On the Russian side of the border with Donbas territory governed by pro-Russian separatists, the Novoshakhtinsk oil refinery caught fire. There was no immediate statement from the Ukrainian government over the incident.

The social media video showed a drone flying towards a refinery, followed by a big ball of fire and thick black smoke billowing into the June sky. Interfax cites the local emergency agency as saying no one was injured and the fire was extinguished.

Ukraine does not often comment on claims of attacks on Russian infrastructure close to the border. In the past, it has referred to similar occurrences as "karma" for the Russian invasion of Ukraine.

Wednesday is "Day of Remembrance and Sorrow" in Russia and Ukraine, commemorating the day Hitler's Germany attacked the Soviet Union. During World War II, an estimated 27 million Soviet civilians perished.

President Vladimir Putin was anticipated to place flowers at a memorial flame in Russia. The Second World War features prominently in Russian propaganda over the invasion of Ukraine, which Putin refers to as a "special operation" to ferret out "Nazis."

Kyiv and the West perceive this as a bogus rationale for a conflict to reestablish Moscow's control over Ukraine's neighbor and eradicate Ukraine's national character.

"Detonated at 4:30 a.m. The word "war" has been prohibited. Accused other nations of hostility. Mykhailo Podolyak, an adviser to the Ukrainian president, tweeted: "Psychiatrists of the future will examine how, after years of constructing the WWII cult, Russia began recreating the bloody pages of history and every Nazi step."

"The name of the final chapter is known: tribunal."