Tension between Iran and Israel has increased over the past year.

Iran hanged a man who was convicted of killing one of its nuclear scientists, state-run Press TV reported in May.

Majid Jamali Fashi was convicted of the January 2010 killing of Massoud Ali Mohammadi, an Iranian university professor and a nuclear scientist. He was also convicted of spying. Prosecutors accused him of working for the Mossad, and said he was paid $120,000 by Israel to carry out the hit.

Israel typically does not comment on such claims.

The killing was among a series of attacks against Iranian nuclear scientists in recent years.

In January, Iran sent a letter to the United Nations secretary-general alleging that the killings of the scientists were terrorist attacks that followed a pattern. "There is firm evidence that certain foreign quarters are behind such assassinations," the letter said.

Iran's efforts to build a nuclear program have unnerved many world leaders, resulting in condemnation and sanctions from the United Nations. Tehran insists the program is for peaceful purposes.

Israel, which is believed to have its own nuclear arsenal and has expressed alarm over Tehran's hostility toward the Jewish state, has said it may attack Iran to try to stop the country from developing nuclear weapons.