Ukraine 16April2014 2
1 of 35. A fighter jet flies above as Ukrainian soldiers sit on an armored personnel carrier in Kramatorsk, in eastern Ukraine April 16, 2014. Reuters

As Ukraine’s government sent troops to win back control of an airfield from pro-Moscow separatists, Russian President Vladimir Putin said Tuesday that the escalation of this conflict will put Ukraine “on the brink of civil war.”

Ukrainian forces launched a “special operation” against separatists in the eastern part of the country, which has been engulfed in protests against the interim government in Kiev. Troops landed by helicopters Tuesday at an airfield in Kramatorsk in eastern Ukraine, where gunfire was reportedly heard as anti-government protesters are said to have tried to prevent the choppers from landing. Ukraine’s acting President Oleksandr Turchinov announced earlier that the operation began in the north of Donetsk and will be conducted “in stages,” and added that the Kramatorsk air base had been “liberated,” according to Reuters.

Meanwhile, Putin, in a phone call with German Chancellor Angela Merkel, discussed the action taken by Ukrainian authorities, and said that “the sharp escalation of the conflict essentially puts the nation on the brink of civil war,” the Kremlin said in a statement.

Putin later spoke to Israeli Prime Minister Benjamin Netanyahu and said, according to the Kremlin: “The crisis is the result of Kiev’s irresponsible policy, which disregards the lawful rights and interests of the country’s Russian-speaking citizens,” adding that "the inadmissibility of the current regime’s use of armed forces to suppress public protests in southeastern Ukraine.”

Vasyl Krutov, head of the Ukrainian Security Service, said according to Agence France-Presse: "They must be warned that if they do not lay down their arms, they will be destroyed," reiterating that the separatists were getting support from the Russian army’s Main Intelligence Directorate, or GRU.

As clashes escalated in Ukraine, the European Union extended its sanctions against Russia, while the U.S. said that it is “seriously considering" adding to the sanctions it has already imposed against Russian officials after Crimea’s annexation by Russia, BBC reported.

"These are not our people, it's not our war and not our revolution," Sloviansk's mayor, Nelya Shtepa, said Tuesday, according to BBC, adding that the armed men at the barricades "don't hide that they are from Crimea, that they are from Russia.”