Iran's Supreme Leader Ayatollah Ali Khamenei has defended the country's armed forces after it admitted shooting down a passenger plane by mistake.

He said the Revolutionary Guard - the elite unit responsible for the disaster - "maintained the security" of Iran.

Widespread protests and criticism from abroad have put growing pressure on Iran over its handling of the incident.

But the ayatollah tried to rally support as he led Friday prayers in Tehran for the first time since 2012.