Russia continues to conduct military drills near Ukraine's border amid its standoff with the West over what is fast becoming Europe's most serious security crisis in decades. 

The Russian Ministry of Defense on Friday released footage of navy warships carrying out firing drills in the Black Sea and military aircraft patrolling Belarusian airspace as part of its joint "Allied resolve-2022" exercises with Belarus. 

Images also showed strategic air-defense units using surface-to-air missile defense systems in the Leningrad region on Thursday.

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Tensions have flared over Ukraine in recent weeks as Moscow massed troops, tanks and heavy weapons near its neighbor's border, demanding assurances that Kyiv never joins NATO, a condition the Western military alliance has refused to accept.

Moscow said this week it is pulling back its forces, but Western countries say they believe the opposite: more equipment and personnel are arriving and making the sort of preparations seen before an attack.

NATO continues to warn of an imminent Russian attack against Ukraine, but the Kremlin says it has no intention of invading, accusing the West of hysteria over its military deployment. 

Ukraine itself has played down the likelihood that Russia will launch a massive assault soon. "Our intelligence sees every move that could pose a potential threat to Ukraine. We estimate the probability of a large-scale escalation as low," said Defence Minister Oleksii Reznikov to Ukraine's parliament on Friday.  

However, Kyiv forces and Russian-backed separatists have in the last 24 hours reported a significant increase in shelling in the country's east for a second straight day. 

A diplomatic source familiar with the conflict told Reuters that the shelling was the most intense in the east since major combat ended there with a 2015 ceasefire.

Kremlin spokesperson Dmitry Peskov said: "We have repeatedly warned that the excessive concentration of Ukrainian armed forces in the immediate vicinity of the line of demarcation, coupled with possible provocations, could pose a terrible danger."

Washington and other Western allies have claimed such escalations on the ground in Ukraine's east could form part of a Russian pretext to invade, an accusation Moscow denies.

In response to a potential attack, the EU is preparing sanctions against Russia that are expected to be much harsher than those imposed after the 2014 annexation of Crimea.

US President Joe Biden will discuss the situation by phone with leaders of the UK, Canada, France, Germany, Italy, Poland, and Romania, plus the European Union and NATO  on Friday.