Russian President Vladimir Putin vowed military support for embattled Belarusian leader Alexander Lukashenko on Thursday, although it would not be deployed unless unrest there spun out of control.

The remarks were the strongest signal yet that Russia is prepared to use force if needed in Belarus, where mass demonstrations have taken place since an August 9 election that the opposition says was rigged to prolong Lukashenko’s 26-year rule.

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“We have of course certain obligations towards Belarus, and the question Lukashenko raised was whether we would provide the necessary help,” Putin told state television.

“I told him Russia would fulfil all its obligations. Alexander Grigorivich (Lukashenko) asked me to create a reserve police force and I have done that. But we agreed this would not be used unless the situation got out of control.”

The 65-year-old Belarusian strongman’s relationship with Putin had soured ahead of the ballot because Minsk refused closer integration with Russia and even claimed Moscow had sent mercenaries across the border to organise riots.

The Belarusian opposition Coordination Council said Moscow’s move to set up such force violated international law.

NATO chief Jens Stoltenberg said Russia should stay out of the crisis saying it was a “sovereign and independent state.”

Polish Prime Minister Mateusz Morawiecki meanwhile said any Russian intervention would be a breach of international law and the “human rights of Belarusian people, who should be free to decide their own fate”.

But Putin also called on the authorities in Minsk and the opposition to “find a way out” of the crisis peacefully. 

He conceded there were problems in Belarus, saying, “otherwise people wouldn’t take to the streets”.

The Russian leader’s calls for calm came after the European Union and ambassadors of member states in Minsk condemned a crackdown on government critics seeking new elections and Lukashenko’s resignation.

EU nations have also vowed to sanction individuals they say were involved in vote-rigging and the violent crackdown on protesters.