Shocking video appears to show a missile strike at the centre of Ukraine's second largest city on day six of Russia's invasion

A huge explosion can be seen outside the regional headquarter of Kharkiv, a mostly Russian speaking city in northeastern Ukraine.

Kharkiv region head Oleg Synegubov accused Vladimir Putin's regime of war crimes after launching missiles at the city and said its defences were holding up.

He shared a video of an explosion at the regional administration building, which showed passing cars just about making it through the blast.

It appears the building was not directly hit, with some speculating the attack was aimed at a Ukrainian army recruitment centre outside.

Residential areas were also reportedly hit by missiles, with six people injured so far, including a child.

Synegubov said on social media that it was too early to tell the number of casualties from today's strikes.

A monitor displays a projectile striking the regional state administration building, as the Russian invasion continues, in Kharkiv, Ukraine March 1, 2022 in this still image obtained from social media video. State Emergency Services of Ukraine via REUTERS ATTENTION EDITORS - THIS IMAGE HAS BEEN SUPPLIED BY A THIRD PARTY
Cars can be seen just about escaping a giant ball of fire outside the government building (Picture: Reuters)
A view shows the regional administration building, which city officials said was damaged by a missile, in central Kharkiv, Ukraine, March 1, 2022. REUTERS/Vyacheslav Madiyevskyy
The blast hit just outside the building, with some speculating the missile was meant for an army recruitment centre (Picture: Reuters)
A view shows the area near the regional administration building, which city officials said was hit by a missile attack, in central Kharkiv, Ukraine, March 1, 2022. REUTERS/Vyacheslav Madiyevskyy
Kharkiv region head Oleg Synegubov accused Vladimir Putin's regime of war crimes (Picture: Reuters)
A view of the square outside the damaged local city hall of Kharkiv on March 1, 2022, destroyed as a result of Russian troop shelling. - The central square of Ukraine's second city, Kharkiv, was shelled by advancing Russian forces who hit the building of the local administration, regional governor Oleg Sinegubov said. Kharkiv, a largely Russian-speaking city near the Russian border, has a population of around 1.4 million. (Photo by Sergey BOBOK / AFP) (Photo by SERGEY BOBOK/AFP via Getty Images)
A car is left completely burnt out in the square outside city hall (Picture: AFP/Getty Images)

Kharkiv has seen some of the heaviest fighting since the Russian launched its invasion on Thursday.

Ukraine's Foreign Minister Dmytro Kuleba tweeted: 'Barbaric Russian missile strikes on the central Freedom Square and residential districts of Kharkiv.

He said 'Putin is unable to break Ukraine down' and added: 'He commits more war crimes out of fury, murders innocent civilians.'

Many journalists were quick to point out that attacks like this did not look like a 'liberation' of a Russian-speaking city as Putin would like to portray.

It comes after Russia was accused of using vacuum bombs and cluster munitions during its invasion of Ukraine.

Also known as thermobaric weapons, vacuum bombs suck in oxygen from the surrounding air to create a more powerful high-temperature explosion capable of vaporising human bodies.

One Western official said: 'Certainly, if it is used in any built-up area, there is no way you can eradicate the risk of significant civilian casualties.'