An Iranian student leader, Heshmatollah Tabarzadi, has been abducted by unknown assailants as he was leaving a student gathering outside the capital, Tehran.

A statement posted on the Internet by Mr Tabarzadi's children said their father was attacked by several men who said they were policemen as he left the meeting with his family.

They said no arrest warrant was produced.

Mr Tabarzadi is a leader of the pro-reform United Student Front USF and has been arrested several times in the past but released without being charged.

From the newsroom of the BBC World Service