Russian build-up of missiles on Baltic angers Nato
Nato has accused Russia of stoking tensions in Europe by deploying anti-ship missiles to its westernmost Baltic region.
The alliance described President Vladimir Putin's decision to send state-of-the-art Bastion missile-launchers to Kaliningrad, which borders Nato members Poland and Lithuania, as "aggressive military posturing".
In a statement to the AP news agency, it said the Kremlin's move would do nothing to "lower tensions or restore predictability to our relations".
It came shortly after US state department spokesman John Kirby called Russia's plans to permanently deploy its S-400 air missile defence system and ballistic Iskander missiles to Kaliningrad "destabilising to European security".
Kremlin spokesman Dmitry Peskov hit back at Mr Kirby's comments, branding Nato an "aggressive" military alliance.
"Russia does what it has to do. It has every sovereign right to take necessary measures throughout the territory of the Russian Federation," Mr Peskov said.
Viktor Ozerov, chairman of the defence committee in the Federation Council, Russia's upper house of parliament, said Moscow's deployment of the Iskander missiles was a response to the US missile shield in Eastern Europe.
The United States activated the first phase of its land-based missile defence system in Romania in May. Another stage is due to come into operation in Poland in 2018.
Russia has long been opposed to the missile shield, which it calls a danger to its national security. Nato said it is intended to guard against attack by 'rogue' states such as North Korea.
Russia also criticised a report that claimed Russian tankers had smuggled jet fuel to Syria through EU waters in contravention of European sanctions.
At least two Russian-flagged ships made deliveries, an intelligence source with a European Union government told Reuters.
The source said the jet fuel was delivered to war-torn Syria via Cyprus.
Russia's defence ministry said its tankers had been taking the fuel to its forces in Syria and that EU sanctions did not "concern" Moscow.
"Russia, like Britain of late, is not a member of the European Union," read the defence ministry statement, in reference to Brexit.
Tensions also mounted between Russia and Ukraine, after Moscow accused the Ukrainian security service of abducting two of its soldiers near the border between Russian-annexed Crimea and Ukraine.
Kiev said the men, named as Ensign Maxim Odintsov and Junior Sergeant Alexander Baranov by the Russian defence ministry, served in the Ukrainian army before deserting to Russia following Moscow's seizure of Crimea in March 2014.
It said they were detained on Sunday after crossing the Chongar checkpoint into Ukrainian-controlled territory.
Russian foreign minister Sergei Lavrov called the men's capture "an unlawful act of provocation carried out by Ukrainian special services toward Russian citizens on Russian soil".