US federal prosecutors say a New Jersey software developer lived a double life as a “sleeper agent” for Iran-backed militant group Hezbollah, and scouted terror targets in New York City.

Assistant US Attorney Sam Adelsberg said on Monday during the start of his trial that the 45-year-old kept up appearances as a “normal” law-abiding US citizen, while also gathering intelligence and researching targets including Rockefeller Center, Grand Central, all three New York-area airports and other high-volume locations as well as buildings in Boston, Washington DC and abroad in France, Turkey and the Czech Republic from 2000 to 2005.

“He posed as a regular guy” working as a software engineer... but by night he was “a terrorist and spy” he said, adding, “In reality, he was a sleeper agent for Hezbollah ready to strike”.

The attorney added that he moved to the United States in 2000 from Lebanon with a secret mission to apply for citizenship and plan a future attack on behalf of the militant group, designated a foreign terrorist organization, so Hezbollah “could kill Americans if Americans threatened Iran, Hezbollah's main ally”.

Saab -- a US citizen since 2008 -- was arrested by the feds in July 2019 and after being questioned during 11 sessions over several weeks with FBI agents he was charged with several counts, including support for a terrorist group, citizenship fraud, receiving military training from a terrorist group, and fraudulent marriage.

Saab's lawyer Marlon Kirton said his client had long cut ties with Hezbollah and ceased all Hezbollah-related activity and communication in 2005.