All staff who were "inside" the Iranian embassy in Beirut escaped unharmed when an explosion went off outside the building on Monday, ambassador Ghazanfar Rokn-Abadi told Iranian media.

"All colleagues inside the embassy are in full health," the ambassador, Ghazanfar Rokn-Abadi, was quoted as saying by Mehr news agency.

He did not elaborate on his remarks, which came before a Lebanese government source told AFP that an Iranian cultural adviser had died in the blast.

The explosion occurred in southern suburbs of the Lebanese capital, a stronghold of the Shia movement and Iran-ally Hezbollah, killing at least 15 people.