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.
Latin American is also considered a possible target by officials following Hezbollah's planning.
A senior US counter-terrorism official told ABC News, "There are concerns Hezbollah might be ready to do something along those lines."
Three US law enforcement agencies say they have been briefed on the developments by intelligence agencies.
A spokesperson for the Canadian Security Intelligence Service says the agency does not comment on the existence of ongoing intelligence operations.
Officials say the CIA, the NSA, and British and Canadian intelligence agencies began to pick up a steady stream of information - from electronic intercepts, human sources and surveillance - about a possible Hezbollah attack on Feb. 17, just days after the Beirut funeral of Mugniyah where Hezbollah leaders publicly declared they would seek revenge.
"They want to kill as many people as they can, they want it to be a big splash," said former CIA intelligence officer Bob Baer, who says he met with Hezbollah leaders in Beirut last month.
"They cannot have an operation fail," said Baer, "and I don't think they will. They're the A-team of terrorism."
Alarms were first raised in Canada, where as many as 20 suspected Hezbollah members have been under surveillance after as many as four suspected "sleeper cells" were activated, including one known as "Rashedan," intelligence officials tell ABC News. The members also received instruction to send their family members home to Lebanon, according to officials.
Officials have also reported that a known Hezbollah weapons expert was followed to Canada, where he was seen at a firing range south of Toronto, near the US border.
Intelligence officials said the recent Hezbollah activities were being coordinated with the help of Iran's elite Revolutionary Guards.
"Hezbollah would not carry out an attack in the west, or wherever this attack is going to occur, without approval from Tehran," said Baer, the former CIA intelligence officer.
Baer says his Hezbollah contacts told him an attack against the US was unlikely because Iran and Hezbollah did not want to give the Bush administration an excuse to attack.
While US officials say there is no credible information of a Hezbollah attack on American soil, the Homeland Security Secretary, Michael Chertoff, told Fox News two weeks ago, that "they make al Qaeda look like a minor league team."
"Hezbollah remains a threat to security in different parts of the world," said FBI Special Agent Richard Kolko, section chief for the national Press Office.