Security has been stepped up across Israel following bomb attacks on its diplomats in India and Georgia.
Intelligence services were also trying to determine whether Israelis were the intended target of an Iranian man carrying explosives who blew himself up in Bangkok.
Israel blamed Iran for Monday's attacks in India and Georgia. It warned that they were just the first in a wave of assaults on Israeli targets by Iran and its Lebanese proxy, Hezbollah.
"The Iranians and Hezbollah are determined to disrupt Israeli life and to act against Israelis all over the world," Defence Minister Ehud Barak said. "They want to strike at Israelis and we must act against this terror front and continue to brace for other challenges we face."
Hezbollah this week marked the fourth anniversary of the assassination of commander Imad Mughniyeh, who died in a mysterious explosion blamed on Israel.
Iran, meanwhile, has accused the Israelis of being behind a series of assassinations of nuclear scientists and other sabotage of its nuclear programme.
In Israel, a police spokesman said security had been heightened at public places, foreign embassies and offices, as well as Ben-Gurion International Airport. Patrols have been stepped up and police told to be especially vigilant.
In India, investigators were searching for what they called a well-trained motorcycle assailant who stuck a magnet bomb on an Israeli diplomatic car in New Delhi, wounding four people, including one critically.
Israel sent forensic scientists from its police force to New Delhi to participate in the investigation
Iran has denied being behind the attack in India, as well as the foiled bombing of an Israeli diplomatic car in Georgia, which appeared to mirror the recent "sticky bomb" killings of Iranian nuclear scientists that Tehran has blamed on Israel.