Image copyright Getty Images Image caption Zelensky became president in 2016
Ukrainian President Volodymyr Zelensky has warned a group of armed men operating in Crimea of a possible “coup”.
He warned that their activities in the Black Sea peninsula showed they were linked to “Russian Federation authorities”.
Russia annexed Crimea in 2014, prompting European Union sanctions.
The warning came hours after Russian troops took part in military exercises in Crimea .
Mr Zelensky, 57, said the armed group must be stopped.
He was speaking as a delegation of MPs was trying to get into Crimea to meet members of the group, and was turned back by the gunmen, state television reported.
Image copyright Getty Images Image caption Mr Zelensky said he hoped Russia would “lift” its sanctions on Ukraine
In the evening, a spokesman for Mr Zelensky said the president was “very worried” by the operation.
“I hope that the representative of Russia in parliament and president of Ukraine will consider how to achieve the release of our people,” the spokesman said, according to the Interfax news agency.
Foreign Minister Pavlo Klimkin called for calm in a statement issued earlier on Saturday.
“I appeal to all sides to refrain from taking any action that could escalate tensions, because this in turn would endanger all our efforts to seek peaceful settlement of the situation,” he said.
There are currently 1,200 EU members and by extension, about 2 million Ukrainians, according to the EU.
Mr Zelensky, who became president in 2016, tweeted he was “bitterly” aware of what was happening in Crimea.
“I hope [the Russians] understand that this annexation is illegal, [and] will lift their sanctions on Ukraine,” he said.
Image copyright REUTERS Image caption Ukraine is seen as hostile territory to Russia, which annexed Crimea in 2014
At the height of the Ukraine crisis, Russia put combat air and ground forces on high alert in Crimea .
In a joint statement, the defence and interior ministers confirmed the drill, saying it had been intended to test “defences against a real threat, whether in the Russian Federation or any other countries”.
The Russian military had also carried out live-fire drills with multiple rocket launchers, multiple-barrel rocket launchers and short-range artillery near Crimea , state news agency RIA Novosti reported.
According to the Russian Defence Ministry, “assistants and formations” from the government troops’ special forces and those from the defence ministry’s special forces training groups carried out the exercise.
The Ministry’s press service said one of the forces, under the direction of the Vostok battalion , had taken part in the drills.
Ukraine has accused Russia of carrying out clandestine operations in Crimea.
Separatist unrest sparked in March 2014 following the ousting of Ukraine’s pro-Russian President Viktor Yanukovych led to the annexation of Crimea.
Russia has denied charges of involvement in the unrest in Ukraine, including the downing of a Malaysian passenger jet.