TEHRAN, JUNE 21 -- A powerful earthquake devastated Iran's densely populated northern region bordering the Caspian Sea today, killing at least 10,000 people and injuring more than 20,000, Iranian officials said.

The Iranian government said through the national news agency that more than 10,000 people had been killed in the quake, which, according to the Geophysics Center at Tehran University, registered at 7.3 on the Richter scale and struck about a half-hour after midnight. Another strong quake, measuring 6.5 on the Richter scale, rocked the same area 12 hours later. The U.S. Geological Survey measured the main quake at 7.7

Iran's representative to the United Nations, Kamal Kharrazi, said in New York that officials in Iran had told him that the death toll had reached 25,000.

He said by telephone that he had spoken to a headquarters set up in the Foreign Ministry in Tehran and had been informed that there were "25,000 dead and a few tens of thousands injured." Kharrazi added that the casualty figures were likely to rise.

The earthquake was the deadliest to hit Iran since September 1978, when about 25,000 people were killed around the eastern desert town of Tabas in a quake that measured 7.7.

The national news agency IRNA said at least 20,000 people had been injured by today's quakes, which leveled entire towns and triggered landslides that made the region all but inaccessible by land. The northern provinces of Zanjan and Gilan were hit hardest.

Thousands of victims lay buried under tons of rubble, with rescue workers, including several hundred Revolutionary Guards, trying to reach the region.

Iranian television showed young men clawing through debris in Gilan's capital, Rasht, occasionally carrying a victim away on a stretcher. A dam south of the city burst, flooding the area.

"Because of damage to major roads and land routes in Gilan there is no possibility of rescue operations by land, and relief teams are waiting for roads to be cleared," IRNA said. Dozens of rescue vehicles were stuck on the roads, the agency reported.

Using helicopters and other aircraft, rescue workers rushed to the area, but poor weather and waterlogged fields hampered their efforts. The most severely injured were being transported to Tehran for treatment.

The deputy governor of Gilan said 80 percent of the residential and commercial areas of the towns of Loshan, Roudbar and Manjil -- with a combined population of 100,000 -- had been damaged, IRNA said.

Iran's official media said the quake had killed at least 1,500 people and injured 3,000 in the town of Tarom-e Oleya in the neighboring province of Zanjan, where large areas were laid waste.

President Ali Akbar Hashemi Rafsanjani declared three days of official mourning and called on the Iranian people to mobilize for relief and rescue work.

{Iran's spiritual leader, Ali Khamenei, called the disaster a "divine test" and urged the residents of the stricken provinces "to pass this test with pride through patience and cooperation," the Associated Press reported from Nicosia, Cyprus.}

Alireza Bokaei, an official of the Iranian Red Crescent Society, said, "The big problem now is to reach some rural areas, but we know that some villages have been destroyed 90 or even 100 percent."

The Caspian region is a scenic panorama of mountains, fertile lands, dense forests and sandy beaches. About 4 million people live in Zanjan and Gilan provinces. With a combined area of 20,000 square miles, they form the country's bread basket, producing wheat, rice, tobacco, tea and a wide array of fruit.

Many towns and villages were left without drinking water or electricity.

The United States, Britain, Japan, France, Switzerland and the European Community all offered help.

The U.S. government sent a message of condolence to Rafsanjani, a State Department spokesman said in Washington.

Spokesman Richard Boucher said the message expressed U.S. "willingness to provide appropriate humanitarian assistance, if Iran so requests" but that Iran had made no request for aid to the United States.

"We understand that Iran has contacted the U.N. disaster relief office to express a desire for international assistance," Boucher said. The United States has had no diplomatic relations with Iran in a decade.

Iranian television showed the extent of the disaster, carrying footage of miles upon miles of collapsed houses.

Helicopter pilots involved in rescue operations described extensive devastation in Gilan Province. "There is no point between the provincial capital, Rasht, and Loushan, 80 miles to the south, that has been spared by the disaster, as the view from the sky shows," IRNA quoted one of the pilots as saying.

The television said one of the worst-hit towns was Roudbar, where more than 5,000 people were killed or injured. It said 90 percent of the town and surrounding areas had been leveled.

Every house was destroyed, and virtually every resident killed or injured in the towns of Ab-bor and Bouin in Zanjan province.

At least 88 people died in Zanjan's biggest city, Qazvin, which is 90 miles northwest of Tehran.

Tehran Radio said the main quake, centered about 125 miles northwest of Tehran, lasted one minute and shook all of the northern and western provinces.

Many Iranians were still awake when the temblors struck, watching a recorded television broadcast of a World Cup soccer match between Scotland and Brazil.

Buildings shook and windows broke in Tehran, sending frightened residents fleeing into the streets. But there were no reports of casualties or major damage in the capital.

The quake also shook neighboring Soviet Azerbaijan, where the Soviet news agency Tass reported some old buildings damaged but no one injured.

August 1968, Khurasan, Iran: An estimated 12,000 people were killed when a quake struck this northeastern province.

May 1970, Yungay, Peru: Some 70,000 people were killed and 600,000 left homeless by an earthquake and subsequent avalanche that buried this northern city.

December 1972, Managua, Nicaragua: Some 5,000 people died in an earthquake measuring 6.2 on the Richter scale that devastated the Nicaraguan capital.

February 1976, Guatemala City, Guatemala: Nearly 23,000 people died in an earthquake and mudslides north of the capital. The quake measured 7.5 on the Richter scale and left a 200-mile-long fissure eight feet wide and 10 feet deep.

July 1976, Tangshan, China: About 242,000 died in an earthquake that measured 8.2 on the Richter scale.

August 1976, Mindanao, Philippines: An earthquake and an 18-foot tidal wave killed an estimated 8,000 people and left 150,000 homeless.

September 1978, Tabas, Iran: Some 25,000 people lost their lives in an earthquake and aftershocks, measuring up to 7.7 on the Richter scale.

September 1985, Mexico City: At least 10,000 killed by an earthquake measuring 8.1 on the Richter scale.

December 1988, Armenia, Soviet Union: An earthquake measuring 6.9 on the Richter scale killed more than 25,000 people, injured 18,000 and made hundreds of thousands homeless.

SOURCE: Reuter