The Russian defence ministry confirmed the strike.

"This morning, high-precision sea and air-based missiles destroyed an oil refinery and three storage facilities for fuel and lubricants near the city of Odessa, from which fuel was supplied to a group of Ukrainian troops in the direction of Mykolaiv," it said.

At least three huge columns of black smoke and flames rose into the sky over an industrial zone.

The rocket attacks came as Russian forces and appeared to be withdrawing from the country's north after Kyiv warned that Moscow was trying to consolidate troops in the south.

Despite the rocket attacks,there were no casualties, said officer Vladislav Nazarov in a statement from the southern regional command that reiterated a ban on publishing the exact sites under fire or the extent of damage.

"The Odessa region is one of the enemy's priority targets. The enemy is pursuing the sly tactic of attacking sensitive infrastructure."

The city authorities had earlier said the attack caused several fires and some missiles had been shot down by Ukraine's air defence systems

AFP reporters heard explosions in the southwestern city at around 6:00 am (0300 GMT).

On Friday, Ukraine's President Volodymyr Zelensky warned Russia was consolidating and preparing "powerful strikes" in the south, joining a chorus of Western assessments that Moscow's troops were regrouping.

Odessa, a historic city of around one million people, is Ukraine's largest Black Sea port and has escaped the worst of the fighting.

UKraine's whole eastern flank from Crimea, which Russia seized in 2014, to the pro-Moscow enclaves of Donetsk and Lugansk in the Donbas region is occupied by Russian forces, with the exception of the besieged city of Mariupol.