Last summer, a previously unknown group calling itself the Homeland Tigers said it was behind a blast which affected a building above ground at Natanz (most of the sensitive work is underground). Statements were sent to the BBC, as well as others, claiming the group were disaffected Iranians and promising more attacks would come. Many at the time assumed Israel was involved in some way, not least because the country has also been linked to the assassination of Iranian nuclear scientists.
Source link