SLOVIANSK // Five pro-Russian separatists were killed yesterday as the Ukrainian government launched an operation to drive militants out of occupied areas in its east.

Russia responded by announcing military exercises along the border, just hours after Ukrainian troops killed the insurgents.

Statements from president Vladimir Putin and defence minister Sergei Shoigu increased fears of a new incursion into Ukraine.

Russia had warned a day earlier that any attack on its citizens or interests in eastern Ukraine would bring a strong response.

Ukraine’s interior ministry said military and police forces killed “up to five terrorists” while destroying three checkpoints north of Sloviansk yesterday. A government member was wounded, it said.

Stella Khorosheva, a spokeswoman for the Sloviansk insurgents, said two pro-Russian fighters were killed at a checkpoint in Khrestyshche, 10 kilometres north of the city.

The situation was quiet in Sloviansk, but checkpoints inside the city were abandoned and it was unclear where the pro-Russian insurgents manning them had gone.

In Kiev, Ukraine’s acting president accused Russia of backing and supplying the separatists in the east and demanded that Moscow stop its intimidation campaign and leave his country alone.

Oleksandr Turchynov said in an address to the nation that Russia was “coordinating and openly supporting terrorist killers” in eastern Ukraine, where government buildings in at least 10 cities have been seized by gunmen. He said Russia must pull its troops from the border and “stop the constant threats”.

Mr Putin decried Ukraine’s “punitive operation” and threatened Kiev with unspecified consequences.

“If the Kiev government is using the army against its own people this is clearly a grave crime,” he said.

Russia already has tens of thousands of troops stationed in regions along its border with Ukraine.

The latest military exercises will involve ground troops in the south and the west, and the air forces patrolling the border, Mr Shoigu said.

Nato’s deputy secretary general Alexander Vershbow sharply criticised Russia for making “veiled threats” and said Russia should pull its troops back.

The Ukrainian government and the West worry that Mr Putin would welcome a pretext for a military intervention in eastern Ukraine.

Mr Putin denies that any Russian agents are operating in Ukraine, but insists he has the right to intervene to protect the ethnic Russians who make up a sizeable minority in eastern Ukraine.

Earlier in Tokyo, US president Barack Obama accused Moscow of failing to live up to “the spirit or the letter” of a deal last week to ease tensions in eastern Ukraine.

If that continued, Mr Obama said, “there will be further consequences and we will ramp up further sanctions”.

Pro-Russian forces say the interim government has not lived up to the Geneva deal by not making nationalists in Kiev disarm and withdraw from their occupied buildings.

With no appetite in the US for a military response, Mr Obama is largely banking on Mr Putin caving in under economic sanctions against his closest associates.

But the success of that strategy also depends on European nations with closer financial ties to Moscow taking similar action, despite their concerns about an effect on their own economies.

“I understand that additional sanctions may not change Mr Putin’s calculus,” Mr Obama said. “How well they change his calculus in part depends on not only us applying sanctions, but also the cooperation of other countries.”

Sloviansk, a city 160 kilometres west of the Russian border, has emerged as the focus of the armed insurgency in eastern Ukraine.

In the south-eastern city of Mariupol, interior minister Arsen Avakov said his forces had cleared city hall of the pro-Russia protesters who had been occupying it for more than a week.

Mr Avakov did not describe the operation. The Ukrainian city sits along the main road between Russia and Russia’s newly annexed Black Sea peninsula of Crimea.

Yulia Lasazan, a spokeswoman for Mariupol’s police department, said about 30 masked men armed with baseball bats stormed the building in the dark early yesterday and started beating the pro-Russia protesters. Five people were taken to a hospital, she said.

Ukraine is going through its biggest political crisis since the 1991 fall of Soviet Union, set off by months of anti-government protests that led to president Viktor Yanukovich’s flight to Russia in February.

Mr Yanukovych’s removal sparked wide anger in his support base in Ukraine’s east. The insurgents, who claim Ukraine’s interim government consists of nationalists who will suppress the east, are demanding regional autonomy or even annexation by Russia.

Ukraine and Russia reached a deal in Geneva last week to defuse the crisis, but pro-Russian insurgents in the east and right-wing militants in Kiev have defied calls for all sides to disarm and vacate the buildings they are occupying.

* Associated Press