Russian forces mount major offensive on Ukraine's Kharkiv region

Russian forces have launched a major offensive along the front near Kharkiv, Ukraine's second-largest city, the Ukrainian Defence Ministry reported from Kyiv on Friday.

Russian ground troops supported by armour had begun advancing at 5 am local time (0200 GMT) in an attempt to break through the defensive lines, the ministry said.

The target of the attack is reported to be Vovchansk, a town lying on the Russian border some 40 kilometres north-east of Kharkiv.

The attack had been warded off thus far, but the fighting was continuing, the Defence Ministry reported.

There has for weeks been speculation in Ukraine on a Russian summer offensive, with reports that tens of thousands of troops have assembled in the region.

The fact that the news was published by the Defence Ministry rather than the general staff, as is usual, is being taken as a sign of the seriousness of the situation.

"Reserves have been brought up to boost the defence along this section of the front," the ministry said.

On Thursday, Russian planes attacked the front near Vovchansk with glide bombs, and overnight Russian artillery bombarded Ukrainian positions.

Russian military blogger Rybar said the initial aim of the offensive was to expand the combat zone and to identify Ukrainian defensive positions.