Tensions are reportedly high among residents of northern Crimea as long convoys of heavy Russian weaponry continue to be sighted not far from the occupied peninsula's border with the Ukrainian mainland.

Crimean Tatar activists have reported armed checkpoints being erected at scattered sites around the peninsula, and unusually large concentrations of Russian hardware in northern regions.

The border crossing between Ukraine proper and the Russian-annexed peninsula had been shut for several hours on August 7, causing long backups of traffic.

Photos and videos posted on the website of the Crimean Human Rights Group, a local nongovernmental organization, showed Russian military trucks being transported on trains on August 6 near Kerch, an eastern port town that is opposite Russia's Stavropol territory.

Vadim Skibitsky, a representative of the Ukrainian Defense Ministry's military intelligence division, told the online news portal Ukrayinska Pravda that the movement of troops and equipment appeared related to upcoming a major Russian military exercise called Kavkaz 2016 slated to begin next month.

He also tried to play down any immediate danger to local inhabitants.

Russia seized Crimea in March 2014 in the aftermath of the so-called Euromaidan protests in Kyiv, that forced President Viktor Yanukovych to flee.

Moscow later declared it had annexed the peninsula, a move that has been rejected across the globe. Its naval base at Sevastopol is the home for the Russian Black Sea Fleet.

With reporting by RFE/RL's Krym.Realii and Ukrayinska Pravda