MOSCOW (Reuters) - Russian authorities have issued warnings against using Bitcoin, saying the virtual currency could be used for money laundering or financing terrorism and that treating it as a parallel currency is illegal.

"Systems for anonymous payments and cyber currencies that have gained considerable circulation - including the most well-known, Bitcoin - are money substitutes and cannot be used by individuals or legal entities," the Russian Prosecutor General's Office said on February6.

It added that Russian law stipulates that the rouble is the sole official currency and that introducing any other monetary units or substitutes was illegal.

Russia's central bank also said on January 27 that Bitcoin trade was highly speculative and that the unit carried a big risk of losing value.

"Citizens and legal entities risk being drawn - even unintentionally - into illegal activity, including laundering of money obtained through crime, as well as financing terrorism," it warned.

The Prosecutor's General Office said it was working with the central bank and other law enforcement agencies to tighten regulations and prevent legal offences committed with the use of pseudo-currencies.

The Bitcoin community in the United States, far more developed than the one in Russia, has already come under intense scrutiny as authorities crack down on illegal activity carried out using the digital currency.

(Writing by Gabriela Baczynska; Editing by Robin Pomeroy)