TEHRAN: Iranian state television said on Monday that more than 15 people were killed in riots which rocked Tehran, of whom more than 10 were members of "anti-revolutionary terrorist" groups.

The other five who died during Sunday's fierce clashes in the Iranian capital were killed by "terrorist groups," the report said, without elaborating.

"In a suspicious act, five people were killed by terrorist groups and the ministry of intelligence announced that more than 10 of the known members of anti-revolutionary terrorist groups were killed," the state television website said.

Iranian reformist websites said on Sunday that security forces killed a nephew of opposition leader Mir Hossein Mousavi while police confirmed that five people died during the massive anti-government rallies in Tehran.

Key opposition figure Ebrahim Yazdi, who served as foreign minister at the start of the 1979 Islamic revolution, has been arrested at his home, the Rahesabz website reported on Monday.

Yazdi, secretary general of the outlawed but tolerated Iran Freedom Movement, "was arrested at home and taken to an unknown place early Monday morning by security agents," the website said.

"He was summoned to an intelligence ministry office (last) Monday but did not go," it added, without elaborating.