Moscow: Russia accused NATO on Monday of destabilising northern Europe and the Baltics by carrying out drills there and announced new military exercises of its own, increasing tension over the Ukraine crisis.
NATO responded by blaming Moscow for instability in the region and accused it of violating a ceasefire agreement in eastern Ukraine by sending in large deliveries of advanced weapons to pro-Russian separatists.
The recriminations deepened the worst standoff between Russia and the West since the Cold War as the death toll mounts in a conflict that has killed more than 4,300 people.
"They are trying to destabilise the most stable region in the world - northern Europe," Deputy Foreign Minister Alexei Meshkov said of NATO in an interview with the Russian news agency Interfax.
"The endless military exercises, transferring aircraft capable of carrying nuclear arms to the Baltic states. This reality is extremely negative."
Moscow is sensitive to any NATO manoeuvres, especially in countries that were once part of the Soviet Union, and Meshkov said Russia would take "every step" to protect its security.
In a move likely to be seen abroad as more flexing of muscles, Russian announced it would hold more military exercises in 2015 than this year - including one in the Central military district that includes Moscow and another involving Belarus.
Military drills by both Russia and NATO have contributed to the deterioration in relations since the overthrow of a Moscow-backed leader in Ukraine in February, after which Russia annexed Crimea and backed the separatists in east Ukraine.
Baltic states concerned
Asked to comment, the US ambassador to NATO said additional measures taken by the alliance were defensive and meant to demonstrate members` commitment to mutual self-defence.
"If you look at the scale of Russian activities in Crimea, first in Crimea and now in southeastern Ukraine, it`s quite evident that they are destabilising," the envoy, Douglas Lute, told a news conference in Brussels.
Lithuanian Foreign Minister Linas Linkevicius told Reuters Russia was to blame for instability by "carrying out aggression against its own neighbour" in Ukraine, and the Latvian and Estonian defence ministries expressed concern about Russia`s "increased activity in the Baltic Sea region".
Moscow says NATO threatens Russia`s security by offering membership to countries once in the Soviet Union, but NATO says Russia has increased air activity around Europe.
"We see a significant military buildup in and around Ukraine," NATO Secretary-General Jens Stoltenberg added in Brussels. "Large transfers of Russian advanced weapons, equipment and military personnel to violent separatists."
Ukraine said on Sunday a convoy of 106 vehicles had entered its eastern territory from Russia without Kiev`s permission and accused Moscow of send arms to the separatists.
A Ukrainian military spokesman, Andriy Lysenko, said on Monday Russian special forces were now taking part in attacks on Donetsk airport in the east. Moscow denies sending in troops.
Foreign Minister Pavlo Klimkin said in an interview that Europe and the United States should begin supplying arms to his country, as this would deter the rebels.