(Adds casualty estimate)

AMMAN, June 16 (Reuters) - A huge explosion shook the Mezze military airport on the western edge of Damascus on Sunday, and ambulances were seen heading to the compound, a major base for President Bashar al-Assad's elite forces, activists said.

The Syrian Observatory for Human Rights, a monitoring group based in Britain with a network of observers in Syria, said it appeared that a booby-trapped car had exploded at a road block near the airport, killing or wounding around 20 members of Assad's forces.

Video footage taken by activists showed flames rising from the area.

State controlled al-Ikhbariya Television said the explosion "resulted from an attempt to target the Mezze military airport". Activists said Assad's forces had blocked roads leading to the airport.

The compound, which is used by Syria's elite Republican Guards, Special Forces and Air Force Intelligence, also serves as a private airport for the Assad family.

Since the uprising, it has been used to fire rockets and artillery at rebellious Sunni Muslim neighbourhoods on the edge of the capital. (Reporting by Khaled Yacoub Oweis, Amman newsroom; Editing by Kevin Liffey)

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