Vienna, Feb 01 (Agencies): A foreign intelligence report said the control systems of Iran's Bushehr nuclear plant have been penetrated by a computer worm released last year, and is warning of a likely Chernobyl-like disaster once the site becomes fully operational.

Russia's envoy to NATO also has raised the specter of the 1986 reactor explosion in Ukraine, but advised last week the danger had passed.

The report, put forward by a nation closely monitoring Iran's nuclear programme, says such conclusions were premature and based on the "casual assessment" of Russian and Iran scientists at Bushehr.

With control systems disabled by the virus, the reactor would have the force of a "small nuclear bomb," it says further.