At least 18 eighteen people have been killed in a car bombing in the town of Zahedan in southeastern Iran.

The device exploded next to a bus owned by Iran's Revolutionary Guards but it is unclear whether the victims were members of the security forces or civilians working for them.

"In this act 18 Zahedan citizens have been martyred. Rebels and those who create insecurity martyred these people in a terrorist act by laying a trap close to a bus," said Iranian military commander Qassim Rezai.

According to reports, four people were in the car which appeared to be broken down on the roadside.

When the bus approached, the four fled on motorbikes parked nearby and the car exploded.

Zahedan is close to the border with Pakistan and Afghanistan. There are often clashes in the area between security forces and armed groups involved in the drugs trade and smuggling.

© Independent Television News Limited 2009. All rights reserved.