7 March 2014
Last updated at 21:10
There is reportedly a stand-off between what are thought to be Russian soldiers and Ukrainian troops at a military base outside the Crimean city of Sevastopol.
A BBC correspondent says two Russian military lorries are manoeuvring outside, surrounded by armed men.
There is no sign that the base has been seized and no shots have been fired.
Troops wearing Russian uniform without insignia and their supporters have blockaded bases in Crimea since taking control of the peninsula last week.
The Interfax-Ukraine news agency reported that about 100 Ukrainian military personnel were stationed at missile defence base A2355 on Friday evening.
Citing a duty officer and Ukraine’s defence ministry, the agency said a Kamaz lorry had rammed open the gates of the facility and about 20 “attackers” had entered, throwing stun grenades.
The Ukrainian troops immediately barricaded themselves inside a building and their commander had begun negotiations, it added.
The BBC’s Christian Fraser, who is at the scene, said the gates did not appear to have been driven through, and there was no sign that the base had been seized.
There are two trucks from the Russian Black Fleet outside the gates, surrounded by irregular soldiers and a very hostile crowd of pro-Russian demonstrators, he adds.
Two journalists who attempted to take photographs were beaten badly.
The incident comes hours after Russian parliamentarians gave a standing ovation to a delegation of pro-Moscow politicians from Crimea, promising support if they wanted to become part of Russia.
The region is due to hold a referendum on 16 March, on whether to join Russia or remain part of Ukraine.
The vote has been denounced by the interim government in Kiev and Western powers as illegitimate.
A spokesman for Russian President Vladimir Putin said that, despite profound disagreements, he hoped that Russia and the West would not return to the Cold War.