Israeli President Shimon Peres denied that Israel had anything to do with the assassination of yet another Iranian nuclear scientist in Tehran this week.
According to local reports, Mostafa Ahmadi Roshan was killed in a car bomb blast after a motorcyclist allegedly slapped a magnetic bomb on his car. Roshan, 32, was the head of a department at the Natanz uranium enrichment facility.
Several other nuclear scientists were killed in similar attacks in the last couple of years, and Iran filed a complaint with the United Nations against what it called "malicious terrorist attacks" against its nuclear scientists.
Iran's state television quoted Iranian Supreme Leader Ayatollah Ali Khamenei as blaming the U.S. and Israel for the attack. He said the attacks had been "carried out by the planning or support of CIA and Mossad services."
Asked in an interview on CNN if Israel was involved in the attack in Tehran, Peres said "not to the best of my knowledge.
"I know that it is fashionable that whatever wrong happens in Iran, it is the United States and Israel. There is nothing new in this approach," he said.
The West says that Iran is using its civilian nuclear program as a cover up to build a nuclear bomb. Iran denies the charges but announced this week that it would start enriching uranium - which could yield the material to make a bomb - at a new underground facility.
The bomb blast comes at a time of stepped up international sanctions against Iran, which some say could be having an impact.
The Islamic Republic has threatened to close the Strait of Hormuz, through which about 40 percent of the world's trades oil supply passes.
According to the White House, President Obama and Israeli Prime Minister Benjamin Netanyahu spoke by telephone on Thursday about Iran (and the recent Israeli-Palestinian talks in Jordan.)
They discussed "recent Iran-related developments, including the international community's efforts to hold Iran accountable for its failures to meet its international obligations," a statement said.
Ha'aretz, YNET, and The Jerusalem Post contributed to this report.