New satellite images show more Russian forces massing on three sides of Ukraine.

Satellite images collected on Wednesday and Thursday reveal new deployment and positioning of Russian military equipment and troops in multiple locations around Ukraine, including Crimea, western Russia and Belarus, adding to an already ominous buildup that has fueled invasion fears.

The new imagery, released by a Colorado-based space technology company, Maxar Technologies, shows new or additional deployments in three locations in Crimea, the Black Sea peninsula that Russia seized from Ukraine in 2014. Those deployments include troops, vehicles and other equipment in Novoozernoye and Slavne near the western coast, and more than 550 new tents for troops and hundreds of vehicles at a disused airfield in Oktyabrskoe, near the center of the peninsula.

The satellite images also show additional military assets were moved to the Kursk area in western Russia. That puts them near the strategic city of Kharkiv, Ukraine’s second-largest, which has a large Russian-speaking population.

Russia is also conducting naval exercises in the Black Sea and the adjoining Sea of Azov. Ukraine strongly criticized the naval maneuvers on Thursday, with the defense minister, Oleksiy Reznikov, claiming on Twitter that Russia was blocking international waters.

For weeks, Russia has been sending military forces into Belarus, saying the deployment was for joint military drills, including units near Ukraine’s northern border. The exercises began on Thursday and are scheduled to continue for 10 days.

Satellite imagery also shows the arrival of new troops and equipment at the Zyabrovka airfield in Belarus, 14 miles from the Ukraine border. The area showed little activity until the end of January, according to analysis of radar imagery by The New York Times, but the satellite images released on Thursday show the airfield bustling with helicopters, vehicles, troop housing and field hospitals.

The images suggest that Russia has increased its military readiness in the region. That would allow Russia to mount an offensive on short notice should President Vladimir V. Putin decide to do so.

U.S. and NATO officials have said that Mr. Putin appears to be preparing for a full-fledged invasion. Russia continues to dismiss that suggestion, insisting that all troop and equipment movements are for ordinary exercises.