A stand-off involving pro-Russian soldiers at a Ukrainian military base outside the Crimean city of Sevastopol has reportedly ended without incident.
A BBC correspondent saw two lorries from Russia's Black Sea Fleet outside the gates, surrounded by armed men.
But no shots are believed to have been fired, and the men and lorries reportedly left after "negotiations".
Troops wearing Russian uniform without insignia have blockaded bases since taking control of Crimea last week.
The incident came hours after Russian parliamentarians promised to support Crimea if it wanted to become part of Russia.
Crimea's parliament announced on Thursday it would hold a referendum on 16 March on whether to join Russia or remain part of Ukraine.
The vote has been denounced as "illegitimate" by the interim government in Kiev, which took power after President Viktor Yanukovych fled to Russia last month in the wake of mass protests against his government and deadly clashes with security forces.
Russian President Vladimir Putin said he hoped the Paralympic Winter Games, which opened in the Black Sea resort of Sochi on Friday, would help "lower the heat of passions over Ukraine".
The Ukrainian team was represented only by a single athlete carrying the national flag at the opening ceremony.
Valeriy Sushkevych, head of the National Paralympic Committee of Ukraine, said its athletes had debated whether to boycott the Games but had decided to compete unless the "crisis were to escalate".
Journalists beaten
On Friday evening, the Interfax-Ukraine news agency cited a duty officer and Ukraine's defence ministry as saying a lorry had rammed open the gates of the missile defence base A2355 outside Sevastopol and that about 20 "attackers" had entered, throwing stun grenades.
Russia's Black Sea Fleet continued to blockade the Crimean port of Sevastopol, where it is based
In Kiev, the coffin of a man mortally wounded in last month's clashes was brought to Independence Square
Pro-Russian self-defence force members were deployed outside Crimea's parliament building
Ukraine's team was represented by a lone flag-bearer at the Paralympic Winter Games opening ceremony
The Ukrainian troops barricaded themselves inside a building and their commander began negotiations before any shots were fired, it added.
The BBC's Christian Fraser, who visited 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 were two military lorries with Russian number plates outside the gates, surrounded by irregular soldiers and a very hostile crowd of pro-Russian demonstrators, our correspondent adds.
Two journalists who attempted to take photographs were beaten badly.
Later, a Ukrainian officer told a Daily Telegraph journalist that the stand-off had ended after the "talks", and that the Russian lorries and about 30 to 60 Russians troops had withdrawn.
The Pentagon estimates that 20,000 Russian troops may be in Crimea, while the Ukrainian border guards' commander puts the figure at 30,000.
In a telephone call with Ukraine's interim Defence Minister Ihor Tenyukh on Friday, US Defence Secretary Chuck Hagel stressed Washington's firm commitment "to support the Ukrainian people and to the sovereignty and territorial integrity of Ukraine", a spokesman said.
'Mortal danger'
President Putin insists that the armed men are local "self-defence forces", and are not under his command.
But he says Russia has the right to use force to protect Russian citizens and speakers who he says are threatened in post-uprising Ukraine.
His spokesman, Dmitry Peskov, said on Russian state television on Friday: "Can Russia stand idly by when Russians somewhere in the world - especially in neighbouring Ukraine - face mortal danger?"
The BBC's James Reynolds reports from government buildings in Donetsk, eastern Ukraine, a focal point for tension
Calls for talks between Russia and Ukraine mediated by the West "make us smile", he said.
The Russian foreign ministry separately accused the EU of taking an "extremely unconstructive position" by halting talks on easing visa restrictions on Russian citizens and on a new pact to replace the 1997 Russia-EU Partnership and Co-operation Agreement.
Meanwhile, Russia's state-owned energy company, Gazprom, warned Ukraine that its gas supply might be cut off unless its $1.89bn (£1.13bn) of debts were cleared.
Gazprom halted supplies to Ukraine for almost two weeks in 2009, a move that caused shortages in Europe.
Ukrainian officials have said the state has come close to bankruptcy since protesters ousted President Yanukovych at the end of February. Officials say $35bn (£21bn) is needed to get through this year and 2015.
