Iran has rejected an annual U.S. State Department report that called it the world's leading sponsor of terrorism.

State TV on Sunday quotes Foreign Ministry spokesman Hossein Jaberi Ansari as saying the report is "false" and further evidence of the "lack of credibility of reports by the U.S. State Department."

As in many previous years, the report identified Iran as the world's "foremost state sponsor of terrorism in 2015" through its financing, training and equipping of various extremist groups, notably Lebanon's Hezbollah, as well as the government of Syrian President Bashar Assad.

Shiite-majority Iran is helping Iraqi and Syrian forces battle the Islamic State, a Sunni extremist group.

But Tehran has defended its support for Palestinian militant groups, saying they have the right to resist Israel's occupation.