A long-awaited “anti-terror” operation to root out pro-Russian separatists in the east of the country has begun, Ukraine’s acting president, Oleksandr Turchynov, told his parliament on Tuesday.

Turchynov said that troops would be deployed to northern Donetsk near the Russian border. He did not provide precise details, saying only that it would be conducted in a “responsible” and “balanced” manner.

“The goal is to protect citizens from terrorists who are trying to tear this country apart,” Turchynov told parliamentarians.

The insurgents, who are demanding broader autonomy from Kiev and closer ties to the Russian Federation, continued occupying government, police and other administrative buildings in eastern cities despite the expiration on Monday of a government-issued ultimatum to lay down their weapons.

A spokesman for the separatists confirmed that government forces had opened fire on pro-Russian activists in the eastern city of Slavyansk, causing several injuries. He added that the so-called “self-defence forces” were preparing for a wider attack.

In Beijing, Russian Foreign Minister Sergei Lavrov said that any action against pro-Russian protesters by the Ukrainian government would undermine highly anticipated four-party talks in Geneva set for Thursday.

Lavrov denied that Russia itself was seeking to undermine the talks between Ukraine, Russia, the United States and the European Union, Russia’s Interfax news agency quoted him as saying.

He added that claims that Russia was organizing anti-government protests in south-eastern Ukraine were “nonsense,” the agency reported.

During the talks, Lavrov thanked Wang for China’s “unbiased position” on the crisis in Ukraine.

“We appreciate Beijing’s measured and impartial stance on the Ukrainian crisis, as well as China’s manifest understanding of all its manifold aspects, including the historic ones,” Lavrov said in an interview published on Tuesday by the official China Daily newspaper.

Also on Tuesday, NATO Secretary General Anders Fogh Rasmussen was due to discuss the impact of the Ukrainian crisis on European security with EU defence ministers in Luxembourg.

Czech Defence Minister Martin Stropnicky ruled out any intervention by the military alliance in Ukraine, but advocated a “firm” EU response given his country’s proximity to the crisis.

He acknowledged the difficulty of finding a unified position in the bloc, saying that the “perception” of the crisis is “different in the south of Europe and in the north of Europe.” German Defence Minister Ursula von der Leyen called for “level-headedness” ahead of highly anticipated four-party talks. She said the meeting with Rasmussen would be “a clear sign” of unity.