(CNN) New satellite images released by a US-based technology company appear to show continuing Russian military buildup in Crimea, western Russia and Belarus, as pressure continues to mount on Ukraine from three directions, underscoring fears that the Kremlin is planning an incursion into Ukrainian territory.
In Crimea, a large deployment of troops and equipment was observed by Maxar in images collected Thursday, according to Stephen Wood, a senior director at the company. The deployment is at the formerly disused Oktyabrskoye airfield, north of the Crimean capital Simferopol.
Maxar assesses that more than 550 troop tents and hundreds of vehicles have arrived at the site. Other sites in Crimea have also seen an influx of troops and equipment, including at Novoozernoye, where there have been extensive artillery deployments and training exercises.
A new deployment was identified by Maxar for the first time near the town of Slavne on the northwest coast of Crimea, including armored vehicles.
The new deployments in Crimea were observed on the same day that several Russian warships, including large amphibious landing ships, arrived in Sevastopol, Crimea's main port.
The warships are expected to participate in scheduled naval exercises that would block off large parts of the Black Sea and Sea of Azov, raising protests from Ukraine that commercial shipping routes would be choked. The Kremlin has denied that shipping routes will be blocked.
The exercises are part of joint military drills by Russia and its ally Belarus, starting Thursday in Belarus' territory and expected to last 10 days. Moscow's deployment in Belarus is believed to be its biggest there since the Cold War, and the United States has expressed reservations about the buildup of Russian troops in the country, which shares a border with Ukraine.
In Belarus, Maxar observed what it calls a "new deployment of troops, military vehicles and helicopters" at the Zyabrovka airfield near the city of Gomel, some 15 miles (25 kilometers) from the border with Ukraine. It is the first time helicopters have been seen in the area. There also appears to be a field hospital at the site.
Additionally, troops and multiple battle groups remain deployed near the Belarusian city of Rechitsa -- less than 30 miles (45 kilometers) from the border with Ukraine. Previous satellite imagery had shown the establishment of tent encampments near Rechitsa.
When combined with recent videos, they suggest a growing Russian presence in the area, which is some 200 miles (320 kilometers) east of where joint Russian-Belarus exercises got underway Thursday.
Social media videos have shown substantial movements by Russian military units in the past few days to the east of Ukraine, around the cities of Kursk, Rostov-on-Don and Bryansk.
Maxar reports what it calls "a large deployment of troops and military forces" that have "recently arrived at the Kursk training area to the east of the city -- approximately 110 kilometers (75 miles) to the east of the border with Ukraine. "
"Additional equipment continues to arrive in the area and preparations are being made to accommodate more troops and equipment," Maxar said.
As Western nations look for diplomatic avenues to ease the crisis, US President Joe Biden urged Americans in Ukraine to leave the country immediately, warning that things could go sour very quickly.
Speaking to NBC News' on Thursday, Biden said: "It's not like we're dealing with a terrorist organization. We're dealing with one of the largest armies in the world. It's a very different situation and things could go crazy quickly."
"There's not" a situation that could prompt him to send US troops to rescue Americans attempting to exit Ukraine, Biden told NBC, adding, "that's a world war when Americans and Russia start shooting at one another."
HIs remarks came after a frosty exchange in Moscow between UK Foreign Secretary Liz Truss and her Russian counterpart Sergey Lavrov. The latter described their talks as "a dialogue of the deaf," while Truss warned that a Russian invasion of Ukraine would have "massive consequences."
Discussion has turned to the Minsk Agreement, which was hammered out during talks in 2015 but never fully implemented, as a possible way out of the current crisis.
But the Normandy Format -- a four-way conversation between representatives from Ukraine, Russia, Germany and France that has been aimingjoi to broker peace in eastern Ukraine since 2014 -- failed to come to an agreement after nine hours of talks in Berlin on Thursday.
Russia has repeatedly denied it is planning to attack Ukraine, despite Moscow's massive troop buildup in the region. The Kremlin is believed to have assembled 70% of the military personnel and weapons on Ukraine's borders that Russia would need for a full-scale invasion, according to two US officials familiar with Washington's latest intelligence estimates.