MOSCOW, April 24 - Russian President Vladimir Putin said Thursday that the deployment of military forces in east Ukraine by the Kiev authorities was a crime against its own people that will "have consequences".

"If Kiev really began to use the army against the country's population... that is a very serious crime against its own people," Putin said.

If the pro-West Kiev authorities are resorting to force, "it is of course some kind of junta," he said.

"That is simply a punitive measure that will without question have consequences for the people making these decisions, including for our inter-governmental relations," he added, without specifying the nature of consequences.

Foreign Minister Sergei Lavrov said the assault by Ukrainian army on separatist posts near the town of Slavyansk is an "unacceptable" act of violence.

"Use of army, especially with support of radical nationalists against the people is an absolutely unacceptable form of violence, moreover I think that this is a criminal decision," he was reported as saying by Russian news agencies.

He said while meeting with Lebanese counterpart Gebran Bassil that Kiev must take the first step in defusing the crisis, while the United States must "use their influence" on Kiev.

Speaking at an event in Saint Petersburg, Putin also said that the Western sanctions imposed against Russia for the annexation of Crimea from Ukraine were not going to be effective.

"Everyone knows... that no sanctions are effective in the modern world, they never have an intended effect," Putin said, calling them "political".

"It is absolutely not critical," he said. "Though I would not say they are a positive thing either."

Kiev has right to defend its sovereignty: EU

The European Union said Thursday the Ukrainian government has the right to defend its sovereignty, but urged all sides to focus on easing the crisis.

As Russian President Vladimir Putin warned that Kiev military operations in eastern Ukraine would have "consequences", Brussels said all efforts must be made to implement last week's Geneva accord.

"We have full confidence in the Ukraine government to implement the Geneva accord," said EU foreign affairs chief Catherine Ashton's spokesman Michael Mann.

"We recognise Ukraine's right to take legitimate action to defend its sovereignty and territorial integrity."

Mann said all parties to the Geneva accord -- Brussels, Washington, Moscow and Kiev -- should "do their utmost (so) that the situation is de-escalated."

He pointed out that the parties had committed to "use their influence" to disarm militias and help restore government control over buildings and areas they have seized.

"Recent events do indicate that in certain cases ... not everybody is determined to follow up" the accord, he said, adding that a diplomatic solution was the only way forward.

Asked about the prospect of tougher sanctions against Moscow if the crisis worsens, Mann said the EU was working on possible new measures but their imposition depended on events on the ground.

"There are no hard and fast deadlines," he said.

The European Union has so far imposed visa bans and asset freezes on nearly 40 Ukrainian and Russian officials and business leaders, including members of Russian President Putin's inner circle.

EU leaders have also agreed to study tougher measures, including outright economic measures, but divisions within the bloc have so far held up a decision.