Firefighters head towards a blaze at a factory after a Russian attack, on the outskirts of Kharkiv, Ukraine, on April 15. (Felipe Dana/AP)

Russian attacks have intensified in various locations in eastern Ukraine, including Kharkiv, Lugansk and Donetsk, according to Ukrainian military and regional officials.

Russian forces appear to be heavily bombarding areas of the three regions ahead of a planned ground offensive.

Around Slobozhansky, which is an area south of Kharkiv, “the Russian enemy is mainly focused on regrouping and building up troops,” the Ukrainian Armed Forces General Staff said.

Russian forces aim to blockade the city of Kharkiv, which continues to come under persistent shelling, and have concentrated up to 22 battalion tactical groups around Izium, the General Staff added. A battalion tactical group normally consists of around 1,000 men.

“The enemy’s main efforts are focused on maintaining previously occupied positions,” he said, noting the deployment of additional Russian units.

In the Donetsk region, Russian efforts focused on capturing the towns of Popasna and Rubizhne, while establishing full control over the strategic port city of Mariupol, he added.

The General Staff also spoke of constant fire against Ukrainian positions around Popasna, saying that Russian forces “are trying to improve the tactical situation, to advance deep into the Popasna settlement”, but were ultimately foiled. .

He reported increased shelling around the city of Severodonetsk, “in order to inflict casualties, exhaust our troops and possibly prepare for offensive operations”, as well as shelling further south in Toretsk.

One person was killed in Kreminna, just northwest of Severodonetsk, a local official said.

Efforts continue to bring residents of the towns of Rubizhne and Kreminna to safety amid heavy fighting in the region, said Serhii Haidai, head of the Lugansk regional administration. He added that there was no water or gas in Severodonetsk.

Over the past day, 10 Russian enemy attacks were repelled in the Donetsk and Luhansk regions, the General Staff added.

“The main events that we will talk about in the days, or rather weeks to come, will be events related to the fighting in the Ukrainian Donbass,” Vadym Denysenko, an adviser to the Ukrainian Interior Ministry, said on Saturday.

Russian missile attacks have spread to other areas beyond the Donbass region, according to Ukrainian officials.

One person was killed in an attack on a village near the city of Poltava, said Dmytro Lunin, the head of Poltava’s military administration.

The country’s top general said he spoke with the top US military official on Friday.

Valery Zaluzhny said he discussed “the heavy fighting on the Kharkiv-Izium border, the deterrence of the Russian offensive in the Luhansk and Donetsk regions, the critical situation around Mariupol and the rocket fire throughout the Ukraine,” with Chairman of the Joint Chiefs of Staff, General Mark Milley.

“I reiterated the Ukrainian Armed Forces’ urgent needs for armaments and ammunition to strengthen our defense capabilities,” Zaluzhny added.

The news comes as Russian preparations continue in eastern Ukraine for an offensive operation.