Commercial satellite images published by a private U.S. company show new Russian military deployments at several locations near Ukraine, suggesting that Moscow’s force buildup continues amid a flurry of diplomacy aimed at easing the crisis.

Russia is holding joint military exercises in ex-Soviet Belarus as well as naval drills in the Black Sea, part of a surge of military activity near Ukraine that has fuelled fears of an impending invasion. Russia denies any plans to attack.

U.S.-based Maxar Technologies, which has been tracking the buildup of Russian forces for weeks, said images taken on Wednesday and Thursday showed significant new deployments in several locations in annexed Crimea, western Russia and Belarus.

The images could not be independently verified by Reuters.

In Crimea, which Russia annexed from Ukraine in 2014, Maxar said it had identified a large new deployment of troops and equipment at Oktyabrskoye airfield north of the city of Simferopol, including 550 troop tents and hundreds of vehicles.

New troops and equipment also arrived near Crimea’s Novoozernoye, it said, pointing also to a new deployment near the town of Slavne, on the northwest coast of the peninsula.

In Belarus, the site of major joint drills, Maxar said it had identified a new deployment of troops, military vehicles and helicopters at Zyabrovka airfield near Gomel, less than 25 km from the border with Ukraine.

In a statement sent by email late on Thursday, it said a large deployment of troops and forces had recently arrived at the Kursk training area in western Russia, approximately 110 km to the east of the Ukrainian border.

Russia has not disclosed how many troops it has deployed and says it has the right to move forces around on its territory as it sees fit. It insists they pose no external threat.