Thousands of mourners in Iran chanted "death to Israel" and "death to America" during the funeral of slain nuclear expert Mostafa Ahmadi Roshan, Friday.

Last week, two men on motorcycles planted a magnetic explosive on the car of Roshan, a chemistry expert and director of the Natanz uranium enrichment facility in central Iran.

Iranian officials have accused America and Israel of orchestrating the attack. They say the assassination was part of a secret operation to stop Iran's nuclear program.
   
Meanwhile, the independent news website, irannuc.ir, reports that the Islamic Republic is preparing a covert counteroffensive against the West.

"Iran's intelligence community is in a very good position to design tit-for-tat operations to retaliate for assassinations carried out by Western intelligence services," the website quoted an unidentified security official.

"Iran's response will be extraterritorial and extra-regional. It follows the strategy that none of those who ordered or carried out (the attacks) should feel secure in any part of the world," the official said.

*Originally aired on January 13, 2012.