SIMFEROPOL, Ukraine (AFP) - Pro-Moscow officials in Crimea on Tuesday launched a website for a weekend referendum on whether to join Russia, saying they had to use a Russian domain name because a Ukrainian one met with resistance.

The peninsula's self-declared prime minister Sergiy Aksyonov, who is pushing for his region to become part of the Russian Federation, announced the website referendum2014.ru in a tweet.

A statement on the website said it had initially launched with a Ukrainian domain name at referendum2014.org.ua but had immediately been subjected to a denial-of-service cyber attack, which it blamed on the new authorities in Kiev.

"This is a restriction of freedom of speech," said the statement signed by "Ukrainian independent journalists".

"We have therefore been forced to switch to a Russian domain until further notice," it said.

"Our portal is aimed at an objective, unprejudiced portrayal of the situation in Ukraine, and at expressing people's feelings and their thoughts on the referendum," it added.

The website's organisers said they had also received an email from the Ukrainian web host server stating that their website had to be shut down because it infringed a law "on the territorial integrity and inviolability of Ukraine" punishable by up to three years in prison.

The Moscow-backed referendum, which will ask Crimeans whether they want to join Russia or have even wider autonomy within Ukraine than it already enjoys, has been condemned as "illegitimate" by the government, and the West has said it will not recognise the result.

An opinion poll published on the website said that 77 per cent of the 1,300 people polled in Crimea this week had said they would vote to become a part of the Russian Federation.

It said there was a 2.6 per cent margin of error.

Eight percent said they would vote for greater autonomy, five percent said they would not take part in the referendum and 10 per cent said they were not sure how they would vote, it said.

Russian forces and pro-Kremlin militants overran Crimea, where Russia's Black Sea Fleet is stationed, in the days after Ukraine's ex-leader Viktor Yanukovych fled to Russia following his ouster on the heels of three months of deadly protests.