Last month, a director of Iran's main uranium enrichment site was killed in a blast from a magnetic bomb placed on his car. The official, Mostafa Ahmadi Roshan, was at least the fifth member of Iran's scientific community killed in apparent targeted attacks in the past two years.
Iran blamed Israel. The official news agency IRNA said later it had "evidence" of alleged U.S. and British involvement in the Roshan killing.
In a signal that Iran could retaliate, Gen. Masoud Jazayeri, the spokesman for Iran's Joint Armed Forces Staff, was quoted by ISNA last month as saying that Tehran was "reviewing the punishment" of "behind-the-scene elements" involved in the assassination.
"Iran's response will be a tormenting one for supporters of state terrorism," he said, without elaborating. "The enemies of the Iranian nation, especially the United States, Britain and the Zionist regime, or Israel, have to be held responsible for their activities."
Iran also has blamed the U.S. and allies for a sophisticated computer virus, known as Stuxnet, that was programmed to disrupt the centrifuges used in uranium enrichment. Iran said the virus was detected in its systems, but claimed no serious setbacks occurred.
In January, a foreign suspect with alleged links to Hezbollah militants led Thai police to a warehouse filled with materials commonly used to make bombs. Police seized more than 8,800 pounds (4,000 kilograms) of urea fertilizer and several gallons of liquid ammonium nitrate at the warehouse in Samut Sakhon, on the western outskirts of Bangkok.
In January 2010, assailants detonated a roadside bomb near a convoy of cars carrying Israeli diplomats in Jordan. No one was hurt, and there was no claim of responsibility.
In 1992, a bombing attack at the Israeli embassy in Buenos Aires killed 29 people. Two years later, a bombing at a Jewish community center in that city killed 85 people.
Argentines have long suspected high-level Iranian diplomats were involved in the 1994 bombing.
Image: Personnel believed to be from the Israeli Embassy, right, inspect the site after an explosion tore through a car belonging to the embassy, injuring two people in New Delhi on Monday.