Iran deactivated the Air defences in Iran's capital, Tehran, to intercept a fresh wave of Israeli strikes, state media IRNA reported a day after Israel initiated a number of attacks on Iran's nuclear programme and military command.

"Tehran's defenses reactivated minutes ago ... to confront Zionist regime projectiles," the official IRNA news agency reported, as an AFP correspondent reported hearing loud blasts and seeing a red blaze in the sky.

The U.N. warned of serious regional and global consequences following Israel and Iran's exchange of airstrikes, urging restraint and renewed diplomatic efforts.

"The impact of these attacks has already been felt throughout the region, with neighboring countries closing their airspace and putting their security forces on high alert," the U.N. Under Secretary-General for Political and Peacebuilding Affairs Rosemary DiCarlo told a Security Council emergency session on Iran.

DiCarlo reaffirmed U.N. Chief Antonio Guterres' "condemnation of any military escalation in the Middle East" and noted the "obligation of Member States, in accordance with the U.N. Charter and international law, not to use force against the territorial integrity or political independence of any state."