Russian forces have launched a major offensive along the front near Kharkiv, Ukraine’s second-largest city, the Ukrainian Defence Ministry reported from Kiev on Friday. Russian ground troops supported by armoured vehicles had begun advancing at 5 am (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. Unidentified sources in the Ukra…