Israeli intelligence chiefs told the cabinet on Sunday that Iran and its Lebanese ally Hezbollah had plotted attacks in more than 20 countries over the past two years, the prime minister's office said.

Mossad spy chief Tamir Pardo and Shin Bet internal security chief Yoram Cohen had been called to brief ministers on "counter-terrorism activity by the intelligence services" following Wednesday's bombing in Bulgaria that killed five Israeli tourists and their driver, and which Israel blamed on Iran and Hezbollah.

"Iran and Hezbollah made preparations to carry out attacks in more than 20 countries around the world over the past two years," said the statement from Prime Minister Benjamin Netanyahu's office.

Netanyahu responded by praising the work of the two intelligence services.

"It is very important to be able to prove to the world that Iran and Hezbollah are behind this wave of attacks on every continent," he was quoted as saying.

"This wave of Iranian attacks carried out through its Hezbollah proxy has met with, and will continue to meet with, a determined response."

No one has yet claimed responsibility for the Bulgaria bombing, which was the deadliest on Israelis abroad since 2004.

Israel, in blaming Iran and Hezbollah for Wednesday's bombing, said it fitted a pattern of other attacks or attempted attacks on Israelis including in Thailand, India, Georgia, Kenya and Cyprus.

Iranian foreign ministry spokesman Ramin Mehmanparast denied any involvement, saying Tehran condemned "all terrorists attacks."

Iran has in turn accused Israel of carrying out deadly attacks on its nuclear scientists. Shiite militant group Hezbollah has also blamed Israel for the killing of one of its commanders, Imad Mughniyeh, in a Damascus car bombing in 2008.