A visiting Russian parliamentarian said earlier on Tuesday that Moscow would act in the event of heightened tension over the Crimean peninsula.

"If the life and health of our compatriots is under threat, we will not stand to one side," the parliamentarian, Leonid Slutsky, said after arriving in the regional capital of Simferopol for a one-day visit.

Slutsky, who leads the Russian Duma's committee for relations with former Soviet states, declined to say what sort of action Russia might take.

AFP reported that two armoured personnel carriers were deployed near Russian military installations in Ukraine's second port of Sevastopol on Tuesday. One of the vehicles was on a base belonging to Russia's Black Sea fleet while another was parked in the courtyard of a navy building in the city centre. A spokesman for the fleet in Sevastopol refused to comment on the deployment of the vehicles but local media reported that they had been sent out in case of "terrorist attacks".