"Witnesses report that large groups of Russian military hardware have been massed near Armyansk and Dzhankoy. Dzhankoy has been cordoned off by troops with tanks and other equipment," Deputy Chairman of the Crimean Tatar Mejlis Nariman Dzhelalov wrote on Facebook on Sunday.

According to earlier reports, the occupying authorities in Crimea blocked the checkpoints at the administrative border with mainland Ukraine on Sunday morning.

"At about 07:00 local time today [Sunday, August 7], the Russian occupying authorities suspended, for unknown reasons, the handling of citizens and vehicles crossing the administrative border with Crimea," the press center of the State Border Service of Ukraine told UNIAN on Sunday.

Further, the State Border Service said that the suspension was the reason why the Ukrainian side halted the work of the checkpoints at Kalanchak, Chaplynka, and Chonhar.