Ukraine makes gains near Kharkiv

Fastest advance since Kyiv pullout a month ago

Ukrainian forces destroyed a pontoon bridge and parts of a Russian armoured column in the Donbas region, video released by Ukraine's military showed on Friday, and a Russian navy ship was set afire in the Black Sea.

Ukraine has driven Russian troops back from the second-largest city of Kharkiv in the fastest advance since Kremlin forces pulled out of Kyiv and the northeast over a month ago.

Ukraine is now in control of territory stretching to the banks of the Siverskyi Donets River, around 40 kilometres east of Kharkiv. The city, which had been under fierce bombardment, has been quiet for at least two weeks but fighting continued to the north.

Russia, which denies targeting civilians, said its forces had shot down a Ukrainian Su-27 aircraft in the Kharkiv region and disabled the Kremenchuk oil refinery in central Ukraine.

Britain said that southeast of Kharkiv, Ukraine had stopped Russian forces crossing the Siverskyi Donets river west of Severodonetsk. Footage released by Ukrainian Airborne Forces Command appeared to show several burned-out military vehicles and segments of a bridge partially submerged in the river and many other damaged or abandoned vehicles, including tanks, nearby.

The British defence ministry said Russia was investing significant military effort near Severodonetsk and Izium, and trying to break through toward Sloviansk and Kramatorsk to complete its takeover of the industrial Donbas region.

Russia-backed separatists said they had taken the Zarya chemical plant in Rubizne near Severodonetsk.

On the humanitarian side, Ukraine accused Russia of forcibly deporting more than 210,000 children so far, saying they were among 1.2 million Ukrainians transferred against their will.

The Kremlin says people come to Russia to escape fighting.

In the southern port of Mariupol, Russian forces intensified bombardment of the Azovstal steelworks, the last bastion of Ukrainian defenders in a siege of more than two months.

Deputy Prime Minister Iryna Vereshchuk told 1+1 television negotiations were underway for the evacuation of wounded troops.

Renewed fighting around Snake Island in recent days may become a battle for control of the western Black Sea coast.

Ukraine said it had damaged a Russian navy logistics ship near the island, a small but strategic outpost close to Ukraine's sea border with Romania.