Thousands of mourners have gathered in central Iran's capital following the killing of Supreme Leader Ayatollah Ali Khamenei in the opening strike of a massive attack by the United States and Israel.

The mourners, who assembled on Sunday in Enghelab (Revolution) Square, dressed mostly in black and some crying, waved Iranian flags and held photos of Khamenei as the US-Israeli assault entered its second day.

Khamenei, Iran's supreme leader since 1989, was killed as the two powers sought to overthrow the Iranian government.

Iranian state television confirmed Khamenei's death early on Sunday, hours after US President Donald Trump announced the killing of the 86-year-old cleric he described as "one of the most evil people in history".

The Islamic Revolutionary Guard Corps (IRGC) pledged "severe, decisive" punishment for Khamenei's "murderers" in a statement.

The IRGC added that it would launch the "most ferocious" operation in history against Israel and US bases, which are located in Gulf countries already counting the cost of an unprecedented series of deadly Iranian strikes.

Trump threatened that any retaliation would lead to Iran being hit with a force that has "never been seen before".

Meanwhile, more explosions were heard in Doha, Dubai, and Manama on Sunday, and warning sirens sounded in central Israel, with the Israeli military saying it was responding to Iranian missile fire.

Source: www.aljazeera.com