Dozens of troop carriers and missile launchers sit on flatbed wagons lining up along tracks running through southern Russia, in a region bordering Ukraine.
Tanks are parked in columns beside the railway, which runs parallel to the M4 highway. Military trucks rumble past, heading toward the southern city of Rostov-on-Don, close to the border.
Ukraine and Western countries accuse Russia of sending troops and heavy weapons to support proxy fighters who seized a swathe of the eastern Donbass region in 2014.
Moscow denies it is part of the conflict in eastern Ukraine and says it provides only humanitarian and political support to the separatists.
The recent deployment of hardware close to Ukraine’s border is seen as a deliberate show of force at a time of rising tensions between the former Soviet states.
Reuters reported that skirmishes were increasing around the separatist-held city of Donetsk, and Kyiv has reported that five of its soldiers have been killed in fighting there this week.
— Based Finland 🇫🇮 (@Based_Finland) April 1, 2021
In recent weeks, Ukraine has displayed caution.
Since the build-up, it has said it is ready to defend itself against any attack in its eastern Donbass region, a mainly Russian-speaking area that fell to pro-Russian separatists who attacked in 2014.
Kyiv says 14,000 people have been killed in the fighting.
Washington and the NATO alliance have accused Russia of a “provocative” build-up, with unverified images of army trucks and missile launchers, taken from the ground and by satellite, widely circulating on social media.
For its part, Russia accuses Ukraine of unspecified provocation and says it can move military assets around its country as it sees fit.
Ukraine is no military match for Russia and it sits outside the NATO alliance. Kyiv lost its Black Sea region of Crimea to Russian troops in 2014 without a fight.
Ukraine turns to the United States and the European Union for support against Russia, but beyond sanctions it is unclear what it can expect from its Western allies. Many years of lobbying for NATO membership have yet to bear fruit.
For Russian President Vladimir Putin, the threat of further economic sanctions by the West looms if countries deem Russia responsible for stoking the conflict.
Russian state banks and oil firms have been hit hard with U.S.-led sanctions, and, while reserves remain healthy at $575 billion, they could take a significant hit if the punishments are harsh.