U.S. officials are warning that Russia could invade Ukraine in a matter of days. Russia says its buildup of troops and weapons is part of planned military exercises. Satellite images, social media videos and photos show the scale and intensity of some of Russia’s latest deployments. The situation is volatile, and Russia’s military movements continue to cause fear and confusion. Satellite imagery from Sunday shows the arrival of new equipment, and vehicles being repositioned at a site just 17 miles from Ukraine. U.S. officials and independent military experts say at least half of Russia’s battalion tactical groups, which are designed for ground combat, have been deployed near Ukraine. Vehicles transporting short-range ballistic missile systems called Iskanders appear to be moving closer to the border, as seen here in Western Russia in February. Satellite images show that these types of weapons were also moved to a site in Belarus in January, putting them within range of Ukraine’s capital, Kyiv. And in mid-February, there was a new addition to the site: a field hospital. Another field hospital was also set up in Crimea, the part of Ukraine that was seized by Russia in 2014. In the same area, satellite images show a new camp for troops, which could indicate a higher level of military readiness. And in Belarus, videos show this Krasukha-4, one of Russia’s most powerful electronic warfare systems, about 50 miles from Ukraine. It has a range of up to 186 miles, and is typically used to interfere with military aircraft radar systems. Russia has also deployed helicopters, and more than half of these ground-attack aircraft recently arrived at an airfield in Belarus. It is also moved landing ships from Northern Europe that can transport tanks, armored vehicles and troops. Russia says 30 of its ships are taking part in live-fire exercises, but the fleet is also effectively blocking Ukraine’s ports, and further encircling the country.