Mr Yanukovich, who fled to Russia last month, also appealed to the armed forces to defy any "criminal orders" handed down by his foes.
In a defiant statement delivered in Russia, Mr Yanukovich attacked what he called the "band of ultranationalists and neo-fascists" that have replaced his government in Kiev and criticised their Western backers.
He said: "I want to ask the patrons of these dark forces in the West: Have you gone blind? Have you forgotten what fascism is?
"I am certain the officers and soldiers of Ukraine know what you are worth and will not carry out your criminal orders."
Mr Yanukovich made his appeal to the army after Ukraine's acting president Oleksandr Turchynov told parliament of plans to raise a new national guard to protect against internal and external threats.
The ousted president said Ukraine's current leaders "want to include fighters from nationalist organisations into the armed forces, put weapons in their hands" and "unleash civil war".
In only his second appearance since fleeing Ukraine, Mr Yanukovich said a presidential election on May 25, which Western governments hope will help cement the political change in Ukraine, would be "illegal and illegitimate", and he would return to Kiev "as soon as circumstances allow".