DUBAI- Iran will hand over Nizar Zakka, a Lebanese citizen and holder of U.S. residency who was detained in 2015, to Lebanon's Hezbollah, the semi-official Fars news agency said on Monday, citing an unnamed source.

"The move would take place in the next few hours. This is done solely because of the respect for and dignity of Hassan Nasrallah (Iran-backed Hezbollah's leader)," the source told Fars.

Lebanon's internal security chief Abbas Ibrahim was in Tehran to negotiate Zakka's release, a senior security official said.

Zakka will be freed late on Monday or on Tuesday, the official said.

Zakka, an information technology expert who has permanent residency in the United States, was sentenced in Iran to 10 years in prison in 2016 and fined $4.2 million for "collaborating against the state".

He had been invited to Iran by a government official in 2015 but disappeared after attending a conference in Tehran. State media announced later that year that he had ties to U.S. military and intelligence services and had been detained by the Revolutionary Guards.

(Reporting by Tuqa Khalid; Additional reporting by Laila Bassam in Beirut; Editing by Raissa Kasolowsky and Ed Osmond) ((Tuqa.Khalid@thomsonreuters.com; +971521047568;))