“When Ukrainians kill Ukrainians I believe this is as close to a civil war as you can get,” Lavrov said in an interview with Bloomberg television.

Lavrov added that “in east and south of Ukraine there is a war, a real war, with heavy weaponry used.

“And if this is conducive to free and fair elections then I don’t recognise what free and fair is.”

Ukraine is due to hold crunch presidential elections on May 25.

But the fragile transitional government in power since the ouster of Ukraine’s pro-Russian leader Viktor Yanukovych in February is leading an offensive against separatists mainly in the east of the country.

Lavrov meanwhile added that the rebels should be included in Western-sponsored roundtable “national unity talks” that got underway on Wednesday.

“We believe that for this national dialogue to succeed it is absolutely necessary to ensure equal participation of all regions of Ukraine,” he said.

This included not only separatists in the east and south “but also the regions of the west where we also have some issues related to self-determination of minorities.”