Satellite imagery taken on Sunday shows a large deployment of Russian ground forces including tanks moving in the direction of the Ukrainian capital Kyiv from approximately 40 miles (64 km) away, a private U.S. company said.
The American company Maxar Technologies Inc. has been tracking the buildup of Russian forces for weeks.
The images released by Maxar showed a deployment comprised of hundreds of military vehicles and extending more than 3.25 miles (5 km). The convey was situated northeast of the Ukrainian city of Ivankiv and contained fuel, logistics and armored vehicles including tanks, infantry fighting vehicles and self-propelled artillery.
The satellite images also showed damage caused by recent airstrikes on the Antonov airport in Hostomel, and heavy fighting in and near the airport, Maxar reported.
As of Sunday, the Russian invasion of Ukraine has led to the death of 352 civilians, including 14 children, according to Ukraine's health ministry. Additionally, 1,684 people, including 116 children, have been wounded.
Since the start of the Russian offensive Thursday, the Russian military has hit 1,067 Ukrainian military facilities, including 27 command posts and communication centers, 38 air defense missile systems and 56 radar stations.
Also, Sunday was the first time Russian military officials mentioned casualties on their side. Although numbers weren't specified, Russia said its losses on its side were far fewer than on the Ukrainian side. Ukraine has claimed that its forces have killed over 3,500 Russian troops and destroyed dozens of armored vehicles and aircraft.