An Associated Press photographer counted at least five bodies after the blasts in south Beirut. A security official, speaking on condition of anonymity in line with regulations, said the explosions killed seven and wounded more than a dozen.
It was not immediately clear what had caused the explosions, and local reports said the blasts were caused by two car bombs.
The main, black gate of the Iranian embassy was blown out and there was damage to the three-story facility. It was not known if anyone inside was hurt.
Debris was scattered on the street and cars were on fire as people ran away from the chaotic scene. The second blast was meters (yards) away from the embassy.
An armed guard of the Iranian embassy told AP that the first blast was believed to have been carried out by a suicide attacker who rode a motorcycle and blew himself up outside the gate. The other explosion, which caused much more damage, was a car bomb, the guard said.
A charred motorcycle stood outside the embassy gate in south Beirut's upscale neighbourhood of Janah, a Hezbollah stronghold.
TV footage showed at least two dead people in the street nearby. Other wounded men covered with blood were seen across the street from the embassy.
The predominantly-Shiite south Beirut has been targeted in the past months with car bombs and rockets in what Syrian rebels say is retaliation to the militant Hezbollah group's involvement in the battles alongside President Bashar Assad's forces in Syria's civil war.
Iran has been one of Assad's strongest supporters, supplying him with money and weapons since the Syrian crisis began in March 2011.