ANKARA

The chief of the NATO military alliance on Monday warned Russia not to make any military moves against Ukraine, saying the cost would be dear.

"Any future Russian aggression against Ukraine would come at a high price. And have serious political and economic consequences for Russia," NATO Secretary General Jens Stoltenberg told reporters ahead of a meeting of NATO foreign ministers in Latvia's capital Riga starting tomorrow.

The two-day meeting is set to discuss a range of issues, including the Russian military buildup near the Ukrainian border.

"We are also monitoring the situation at the border of Ukraine with concern. This is the second time this year that Russia has amassed large and unusual concentration of forces in this region,” Stoltenberg told a press conference alongside Egils Levits, president of the Baltic state of Latvia.

“We see heavy weapons, artillery, armored units, drones and electronic warfare systems and tens of thousands of combat-ready troops.”

He stressed that Russia has to show transparency in order to reduce tensions and de-escalate the situation.

"NATO's approach to Russia remains consistent. We keep our defense and deterrence strong, while remaining open for dialogue with Russia," he said.

Stoltenberg stressed that NATO allies have significantly stepped up their presence in the region in recent years, triggered by Russia's aggressive actions against Ukraine in 2014, with the illegal annexation of Crimea and continued efforts by Russia to destabilize eastern Ukraine, and their support for separatists in Donbas.

"And over the last years, we have actually implemented the largest and the biggest reinforcements of our collective defense since the end of the Cold War, with the four battle groups in the three Baltic countries and Poland, with more naval presence, continued air policing, and also higher readiness of forces. We have tripled the size of the NATO Response Force to over 40,000 troops, that can be deployed on short notice, if needed," he said.

NATO officials say that the Russian military activities in Crimea, which was illegally annexed in 2014, and around the Ukrainian border raise serious questions.

The NATO foreign ministers will also examine the security situation in Afghanistan, Ukraine, and Georgia, as well as NATO's role in promoting stability and security in the Western Balkans region amid rising tensions between Serbia and Kosovo and the separatist ambitions in Bosnia-Herzegovina's Serb entity, the Republika Srpska.

NATO's next Strategic Concept and the alliance's contribution to international arms control will also be addressed.

Some sessions of the meeting will also be attended by foreign ministers of Sweden, Finland, Georgia, and Ukraine, all of them non-NATO states.

Member state Turkey will be represented by Foreign Minister Mevlut Cavusoglu, who is expected to hold a number of bilateral meetings with his counterparts on the sidelines of the meeting.

Fighting between Ukrainian government forces and pro-Russian separatists since 2014 in Donbas has seen more than 13,000 people killed – a quarter of them civilians – and as many as 30,000 wounded, according to the UN.​​​​​​​​​​​​​​