Ukraine crisis and anti-terror operation in eastern cities
A pro-Russian armed man stands guard outside a regional government building seized  in Kramatorsk, eastern UkraineReuters

Russia's foreign minister Sergei Lavrov has warned that his forces in the border region with Ukraine would retaliate if attacked, after Kiev ordered that "anti-terror operations" be recommenced.

In an interview with Russia Today, Lavrov stated that his forces in the bordering region would respond if Russian interests are attacked by Ukrainian forces.

Lavrov said: "If we are attacked, we would certainly respond. If our interests, our legitimate interests the interests of Russians have been attacked directly, like they were in South Ossetia for example, I do not see any other way but to respond in according with international law."

He also insisted that none of the Russian troops in the bordering regions have penetrated the Ukrainian territory, which had previously been claimed by Kiev officials earlier.

In the Donetsk region, the Ukrainian forces have shifted gears entering to the "active phase" of the operations to recapture the state buildings from the pro-Russian separatists.

"Today, the active phase continues. Law enforcement agencies are working to destroy the gangs operating today in Kramatorsk, Slavyansk and other cities of Donetsk and Luhansk regions," Ukraine's First Deputy Minister Vitaliy Yarema told reporters.

Kiev was also spurred by the discovery of the body of Volodymyr Rybak, a local councillor representing Turchinov's political party in the town of Horlivka, who went missing recently. Rybak's body and that of another, yet-to-be-identified man were found in a river near the eastern Ukrainian city of Slavyansk. Both had been tortured.

Both Russia and the US have been accusing each other of meddling with the Ukrainian crisis.

Lavrov took the opportunity to swipe at the US adding: "Ukraine is just one manifestation of the American unwillingness to yield in the geopolitical fight. Americans are not ready to admit that they cannot run the show in each and every part of the globe from Washington alone."