Shots have been reportedly fired from automatic rifles by Russian troops while taking over a Ukrainian naval post in Crimea.
They are said to have broken in to the inland base near the town of Backchisaray at around 2pm (12 noon Irish time). However it is unclear if the weapons were fired in the air - or at the naval post.
No one was injured in the attack and it it understood the Ukrainian commander of the base was trying to negotiate an end to the stand-off.
The development came as Russia said it had drawn up proposals for resolving the Ukraine crisis to send to the US.
Foreign Minister Sergei Lavrov said the proposals aimed to "resolve the situation on the basis of international law and take into account the interests of all Ukrainians without exception" but gave no specific details.
The Minister met with Russian President Vladimir Putin to discuss the creation of an "international contact group" on Ukraine - an idea that has been floated by Germany to increase dialogue between Western powers and Russia.
Mr. Lavrov said he had invited US Secretary of State John Kerry to visit Russia, but his US counterpart wanted to postpone the visit.
US President Barack Obama is to hold talks with Ukrainian Prime Minister Arseniy Yatsenyuk at the White House as part of the diplomatic efforts to resolve the Ukraine crisis peacefully.
Wednesday's meeting sends a clear signal to Moscow that the US considers Mr. Yatsenyuk and his interim government to be legitimate.
The White House said Mr. Yatsenyuk's visit would "highlight the strong support of the United States for the people of Ukraine" in the face of the "ongoing military intervention in Crimea".
It will take place just days before a planned March 16th referendum on whether Crimea should break away from Ukraine and join Russia.
Viktor Yanukovych statement expected
Mr. Yatsenyuk will also be addressing the United Nations Security Council on the situation in Crimea on Thursday. He has said the referendum has "no legal grounds" and has insisted "Crimea is, was and will be an integral part of Ukraine".
However, Mr. Putin insists he has the right to protect Moscow's interests and the rights of ethnic Russians in the Crimean peninsula, where it is believed there are now up to 30,000 troops, believed to be Russian forces.
Russian news agencies also reported ousted Ukrainian President Viktor Yanukovych will make his first public statement in more than a week in Rostov-on-Don, in southern Russia, on Tuesday.
Mr. Putin has rejected the leadership change and removal of Mr. Yanukovych in Kiev as an illegitimate and unconstitutional coup. He was toppled after three months of demonstrations against a decision to spurn a free trade deal with the European Union for closer ties with Russia.
During his last public appearance on February 28th in the same Russian city, he insisted he was still the legitimate leader of Ukraine.
Rallies are expected to be held in Ukraine's eastern city of Donetsk, raising fears of further clashes between rival pro-Ukrainian and pro-Russian protesters.
Meanwhile the British Foreign Secretary William Hague has been speaking to reporters after a meeting with his Polish counterpart about the situation.
