Russian forces carry out land and naval training in Crimea before President Vladimir Putin arrives following Ukraine's announcement of martial law as tensions increase on the front line.
Russian state-run news agency RIA said on Friday that Russian forces were carrying out logistics training in Crimea, citing the Russian defence ministry.
Russian President Vladimir Putin also visited Crimea on Friday to convene a meeting of his Security Council. Putin is also due to speak with Moscow-backed officials in the territory.
His visit came amid talk of relations between Ukraine and Russia being cut, although Putin said that Russia doesn't plan to cut relations with Ukraine.
"We are not going to cut (diplomatic) ties despite the unwillingness of the current authorities in Kiev to have fully-fledged diplomatic ties at ambassador level. We will nonetheless create the possibilities for contacts to develop," he said.
Putin's visit comes during the worst confrontation between Russia and its neighbour Ukraine since a 2015 truce known as the Minsk Agreement - a deal that eased violence between pro-Russian rebels and Ukrainian forces in the country's eastern Luhansk and Donetsk regions- was signed.
Russia, Ukraine, France and Germany were signatories to the agreement.
During his visit, Putin said he and his officials will see what extra security measures can be taken to ensure Crimea was better protected in the future.
Russia illegally annexed the Crimean peninsula in 2014, which led to the US and the EU implementing dozens of sanctions on Russia.
The Crimean drills come just two days after Russia started planned tactical naval aviation exercises involving helicopters serving in its Baltic Fleet, which is based in its European exclave of Kaliningrad.
Kaliningrad is the only Russian territory that has direct access to Baltic Sea, which sits between NATO members Poland and Lithuania.
Martial law looms on the horizon
Ukrainian President Petro Poroshenko said on Thursday Ukraine could impose martial law if the situation in eastern Ukraine worsened.
"If the situation escalates in the east and in Crimea we don't rule out the possibilities (that) we will be forced to introduce martial law and announce a (further) mobilisation," Poroshenko said in a televised speech from the western Lviv region.
Poroshenko did not give further details of the martial law such as a time period or the regions that would see it imposed.
According to Ukrainian law, martial law is passed through a presidential decree that needs to be approved by parliament. Measures could include restricting the movement of people as well as banning political parties and institutions.
Recently, Russia accused Ukraine of killing two Russian servicemen in Crimea in separate incidents earlier this month, but Ukraine rejected the claims.
Poroshenko lashed out the "absolutely irresponsible statements" by Russian, saying that they aim to undermine the Minsk agreement.
According to the UN, more than 9,500 people have been killed in the conflict since it began in early 2014.