SIMFEROPOL, Ukraine (Reuters) - Armed police burst into a hotel in Simferopol, the capital of Crimea, on Saturday night on the eve of a referendum aimed at deciding whether the Ukrainian region leaves Ukraine and becomes part of Russia.

Witnesses saw around 30 men in balaclavas carrying automatic weapons inside the Hotel Moscow, a Soviet-era hotel popular with Western reporters covering Sunday's referendum.

The witnesses said the men burst in brandishing weapons and made their way to the building's fourth floor.

Crimean Defence Minister Valery Kuznetsov told reporters that police were reacting to an alert which turned out to be false.

"We received a false alarm. We came to check," he told reporters at the hotel.

"We have checked everything and it turned out to be bogus. There is an information war going on, being waged by Kiev ... So we have to check everything and be ready for any contingency."

By 9:40 p.m. (1940 GMT) the policemen had started to leave the hotel.

The incident occurred at a time when Russian state media has ratcheted up its anti-Western rhetoric, accusing the West of supporting what it says are fascist elements within Ukraine's provisional government.

Western reporters working in Crimea have complained of harassment by pro-Russian activists in recent days.

Some witnesses at the hotel said the raid appeared to be designed to intimidate journalists on the eve of the referendum.

(Reporting By Aleksandar Vasovic; Editing by Andrew Osborn and Mike Collett-White)