Iran has temporarily released on bail a pioneering Iranian blogger who has been sentenced to more than 19 years in prison, a rights group said on Thursday.

Iranian-Canadian Hossein Derakhshan, held in prison in Iran since 2008 on what the media has said are suspicions of spying for Israel, was freed on Wednesday night on the unprecedented bail amount of $1.5 million, the International Campaign for Human Rights in Iran reported.

Derakhshan, nicknamed the Blogfather and credited with launching a blogging revolution in Iran, was sentenced to more than 19 years in prison in September for cooperating with hostile countries, spreading propaganda and insulting religious figures, according to Iranian media.

The western-based International Campaign for Human Rights in Iran said Derakhshan was expected to return to prison in the next few days.

Derakhshan was a journalist in Tehran before moving to Toronto in 2000. He became famous by publishing instructions on how to use blogging software to publish blogs in Farsi, sparking an explosion of blogging in the Iranian language.

Derakhshan, who was critical of the Tehran government in the past, visited Israel in 2006. Iran does not recognize Israel and Iranians are banned from traveling there.

Iran's hardline rulers often accuse the United States, Israel and other western countries of seeking to overthrow clerical rule through a soft or velvet revolution with the help of intellectuals, internet websites and satellite channels.

(Editing by Elizabeth Fullerton)