KYIV/MOSCOW - Ukrainian President Volodymyr Zelensky on Friday dismissed Air Force commander Mykola Oleschuk from his post, according to a decree published on the presidential website.

"I decided to replace the commander of the Air Force of the Armed Forces of Ukraine," Zelensky said in a statement on Telegram, without giving the reasons for the replacement.

In his statement, Zelensky stressed the need to strengthen the Air Force and protect its personnel.

Later in the day, the General Staff of the Ukrainian Armed Forces said that Lieutenant General Anatoliy Kryvonozhko, commander of the Center Air Command, will temporarily perform the duties of the Air Force commander.

The dismissal was announced just a day after the Ukrainian military reported that an F-16 jet crashed and its pilot died on Monday.

The Ukrainian military did not provide a reason for Monday's crash. Oleshchuk said on Monday partners from the US were helping to investigate the incident.

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A US defense official told Reuters that the crash did not appear to be the result of enemy fire, and possible causes from pilot error to mechanical failure were still being investigated.

The arrival of the first F-16 jets was a milestone for Ukraine.

At least six killed in Ukraine's Kharkiv

Separately, at least six people were killed and 59 others injured in a Russian strike on Ukraine's eastern city of Kharkiv on Friday, according to Kharkiv regional governor Oleg Synegubov.

Russia launched an attack with guided bombs from the Belgorod region, striking five locations, including a 12-story apartment building, Synegubov wrote on Telegram.

Among the victims was a 14-year-old girl, he noted.

The governor added that 20 of those injured are in either serious or critical condition.

Rescuers and emergency personnel are working at the scenes of the attacks, said the State Service for Emergencies.

Five killed in Russia's Belgorod

Five people were killed and 37 others injured after Ukrainian forces attacked Russia's Belgorod region, regional governor Vyacheslav Gladkov said on his Telegram channel Friday evening.

Gladkov said Ukrainian armed forces used cluster munitions from a Vampire multiple rocket launcher system to shell the city of Belgorod and its surrounding areas, causing significant casualties and damage.

"One woman and four men died on the spot from their injuries before the ambulance arrived," the governor said.

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A total of 37 civilians, including six children, were injured in the attack, Gladkov said. All of the wounded have been transported to medical facilities in Belgorod for treatment, among whom seven adults and three children were in critical condition, he added.

According to Gladkov, the assault caused extensive property damage in Belgorod, shattering roofs and windows in two apartment buildings and damaging the glazing and facades of social facilities and commercial properties. A fire ignited by the strike on the outskirts of the city has been extinguished.

The attack also damaged 13 vehicles near a shopping center in the village of Dubovoye, located just to the south of the city of Belgorod, and set two houses, a car and a garage on fire, he said.

With Reuters inputs