DONETSK, Ukraine (USA TODAY) -- Ukraine launched a military operation against pro-Russian separatists Tuesday in a region close to the Russia border despite warnings from Moscow to leave the insurgents alone.
"It will be conducted step by step, responsibly, cautiously," Ukraine President Oleksandr Turchynov told the country's parliament shortly before the operation began.
"The aim of these actions is to protect the citizens of Ukraine, to stop terror, to stop criminality, to stop attempts to tear Ukraine to pieces."
The first visible action of the assault was the retaking by Ukraine troops of a small airfield near the town Kramatorsk, in the East Ukraine region of Donetsk. Russian state television reported that as many as 11 people had been killed but there was no confirmation of any casualties.
Much of the shooting appeared to have been warning shots into the air, said several media reports. The mayor of Kramatorsk said Ukrainian troops had taken control of the airfield. Kramatorsk is about 100 miles from the Russian border, where thousands of Russian military troops, tank columns and fighter jets are based.
Russian President Vladimir Putin has warned Ukraine that he may intercede in the unrest to protect ethnic Russians, though it is ethnic Russians who have been the ones forcing their way into government buildings in 10 cities.
The occupiers are demanding that a referendum be held to secede and join Russia, and they are urging Russian forces to invade as they did in Crimea. The Russian province of Crimea has been overtaken militarily by Putin, who annexed it into Russia despite phone calls with U.S. President Obama who warned him of repercussions should he do so.
NATO Secretary General Anders Fogh Rasmussen met Tuesday in Luxembourg with European Union defense ministers and and told reporters he was "deeply concerned" by the developments in Ukraine.
"I call on Russia to de-escalate the crisis, to pull back its troops from Ukraine's borders, to stop destabilizing the situation in Ukraine and make clear that it doesn't support the violent actions of pro-Russian separatists," he said.
In a phone call Monday, Obama asked Putin to pull back troops from Ukraine's border and persuade armed pro-Russian groups to leave the buildings they have seized. Putin's office said he told Obama that the protests "are the result of the Kiev authorities' unwillingness and inability to take into account the interests of the Russian and Russian-speaking population."
Turchynov accused Russia of fueling the unrest in East Ukraine by infiltrating the country with Russian special forces who are aiding separatists. Russian speaking masked men, well-armed and in matching uniforms bearing no insignias, have been seen helping the occupiers build barricades to keep Ukraine troops from forcing them out.
"Russia wants the whole south and east of Ukraine to be engulfed by fire," Turchynov said. "They want the whole south and east to burn: from Kharkiv to Odesa regions."
Ukraine's government has hinted that it is willing to consider granting more autonomy to regions in the east but not independence. Close to half of the people in the east are ethnic Russians.
But independent polls, one conducted by Gallup last month, show that the majority of people in the east and south do not want to become part of Russia. A majority of Crimeans responded the same way.
"I'm not happy because of these events," said Vladimir Ivaschenko in Donetsk. "I'd like to live in a normal Ukraine and without any influence from Russia or from west side.
"It seems like Russian tanks are going to enter Ukraine. Separatists already called for Russian help," he said.
Others feel the central government in Kiev has not heeded the wishes of populations in the east and it is to blame for the unrest.
"I am worried with our central power and I am worried about a new split between Ukrainians," said Olga Chuvaeva, also from Donetsk. "Western Ukraine always hated Russia. They don't hear us. Here, in Donetsk, we never hated western Ukraine."
An AP reporter earlier reported seeing seeing at least 14 armored personnel carriers with Ukrainian flags, one helicopter and military trucks parked 24 miles north of Slovyansk, which is 100 miles from the Russian border.
Other heavy military equipment appeared nearby, along with at least seven busloads of government troops in black military fatigues.
"We are awaiting the order to move on Sloyvansk," said one soldier, who gave only his first name, Taras.
Two of the helicopters loaded with troops later took off and headed toward Slovyansk.
A CNN news team also reported encountering a large Ukrainian military column traveling on roads leading from the city of Donetsk toward other towns in the region on Tuesday. The column included more than 20 armored personnel carriers, along with support vehicles, and a helicopter circled overhead.
Roads into Slovyansk, a city some west of Russia that has come under ever more secure control of the gunmen since Saturday, were dotted with checkpoints. One at the entrance into town was waving a Russian flag. Another bore a sign reading "If we don't do it, nobody will."
Russia strongly warned Kiev against using force against the pro-Russian protesters, saying Moscow could walk out of an international conference devoted to the Ukrainian crisis scheduled for Thursday in Geneva.
"You can't send in tanks and at the same time hold talks and the use force would sabotage the opportunity offered by the four-party negotiations in Geneva," Russian Foreign Minister Sergey Lavrov said at a press conference Tuesday after talks with Chinese Foreign Minister Wang Yi.
"One cannot issue invitations to talks while at the same time issuing criminal orders for the use of armed force against the people there."
Facing economic stress, Ukraine's central bank increased its benchmark interest rate from 7% to 14.5% to prevent massive inflation due to the record lows of its currency.
Russia's state-owned gas industry has threatened to cut off supplies to Ukraine, prompting German utility company RWE AG on Tuesday to start supplying gas to Ukraine via Poland.
Contributing: Doug Stanglin in McLean, Va., Luigi Serenelli in Berlinb, Associated Press