LONDON -- Several European countries issued warnings Friday against travel to Ukraine's Crimea region.

Britain advised against all travel to Crimea Peninsula and told its citizens now there to leave. The Foreign Office also advised British nationals to avoid the region's Simferopol's airport, where gunmen in unmarked military uniforms were patrolling with assault rifles.

Germany's Foreign Ministry strongly advised against nonessential travel to Crimea, while its counterpart in Italy said travellers should postpone trips "until the situation normalizes." Italy's foreign ministry also urged caution when going out in the evening in Kyiv, Ukraine's capital, and to avoid any demonstrations taking place there.

The warnings came amid reports that airspace over the Crimea Peninsula has been closed.

The situation in Crimea has become tense as masked gunmen have taken control of government buildings, airports, and other strategic sites in the wake of a three-month protest which saw pro-Russian President Viktor Yanukovych pushed from power.

Ukraine has accused the Kremlin of invading Crimea, saying Russian troops have taken up positions around a coast guard base and two airports.

On Thursday Czech Foreign Minister Lubomir Zaoralek said he and fellow diplomats would not travel to Crimea while in Ukraine because of security concerns.