A powerful earthquake rocked the Alborz mountain chain in northern Iran yesterday, killing at least 20 people and damaging scores of villages, officials said.

The United States Geological Survey said the tremor had a magnitude of 6.2 - powerful enough to bring down many buildings.

The quake late Friday afternoon shook the capital Tehran, about 100 km south of the epicentre, where startled residents poured into the streets and some windows were broken.

But Iran's Vice President Mohammad Ali Abtahi said the Islamic Republic was not steeling itself for a big death toll.

Memories are still fresh of an earthquake that devastated the city of Bam, far away in the southeast, on December 26, measuring 6.8 and killing more than 20,000 people.

State media put Friday's epicentre at Chalus, a small town on the Caspian coast on the other side of the Alborz mountains from Tehran.

A government official in Tehran, who declined to be named, put the overall toll at 20 dead and 150 people injured. But separate reports from different provinces in northern Iran suggested at least 28 had been killed.