Intelligence agencies in the United States and Canada are warning of mounting signs that Hezbollah, backed by Iran, is poised to mount a terror attack against "Jewish targets" somewhere outside the Middle East.

Intelligence officials tell ABC News the group has activated suspected "sleeper cells" in Canada and key operatives have been tracked moving outside the group's Lebanon base to Canada, Europe and Africa.

Officials say Hezbollah is seeking revenge for the February assassination of Hezbollah's military commander, Imad Mugniyah, killed by a car bomb in Damascus, Syria.

The group's leaders blamed Israel, an allegation denied by Israeli officials.

There is no credible information on a specific target, according to the officials.

Suspected Hezbollah operatives have conducted recent surveillance on the Israeli embassy in Ottawa, Canada and on several synagogues in Toronto, according to the officials...