A powerful earthquake struck southern Iran on Wednesday near Bandar Abbas, site of a major oil refinery, killing at least four people and injuring 26, officials and state media said.

The U.S. Geological Service said the quake's magnitude was 6.1 and it struck at 1100 GMT about 53 km (33 miles) west-southwest of Bandar Abbas at a depth of 34.6 miles (55 km).

Iran's official IRNA news agency also put the quake at 6.1 on the Richter scale, after earlier Iranian reports had said it could be as high as 7.5. Any quake above magnitude 6 can cause severe damage.

The state broadcaster said two of those injured were in critical condition.

Iran is the world's fourth largest oil exporter and Bandar Abbas is a major port with oil installations including a refinery. An industry official told Reuters last month that Bandar Abbas was processing 320,000 barrels per day of crude.

"Fortunately, there was no damage to the oil industry's facilities at Bandar Abbas," Hojjatollah Ghanimifard, vice president for investment affairs at the National Iranian Oil Company, told Reuters.

Iranian state television quoted a Red Crescent official as saying rescue workers were searching for casualties.

It said 15 people were injured on Qeshm, an island in the southern Gulf close to where the tremor struck. ISNA news agency said the quake cut off power to the island.

PANIC IN STREETS

An Interior Ministry official told Reuters the quake was centred on Bander-e Khamir in the south of the country. "It might have damaged old parts of the place," the official said.

State radio reported people ran panicking into the streets.

A resident of Qeshm island told Reuters he had heard that some homes in villages around the area had been damaged. He had not heard of major damage in big urban areas.

Receptionists at two hotels in Bandar Abbas, contacted by telephone, said the quake had rattled their buildings.

Residents in the United Arab Emirates, across the Gulf from Iran, reported feeling a slight tremor. Bankers and office workers evacuated buildings in Dubai, eyewitnesses said.

A number of seismological fault lines cross Iran. In 2003, about 31,000 people were killed when a quake struck the historic city of Bam, 1,000 km (600 miles) southeast of Tehran.

In March 2006, a magnitude 6.0 quake with aftershocks struck the same province of Hormuzgan in southern Iran, causing only minor damage. In 2005, a 5.9 quake on the Richter scale hit Qeshm island in the Gulf, killing 10 and injuring 50 people.