Updated at 7 a.m. ET

A magnitude 7.3 earthquake that struck northern Iraq and parts of Iran has killed more than 400 people in both countries and injured more than 6,000, according to officials. It is the strongest quake to hit the region in years.

Most of the reports of dead and injured came from Iran, with both state and semi-official news agency saying 407 people are dead and 6,660 others are hurt. The Kurdistan region Ministry of Health says eight people were killed in Iraq — seven in Kurdistan and an eighth in Diyala province. The health ministry said 535 had been injured.

The Iranian province of Kermanshah is the hardest-hit, with Reuters quoting state media as saying there are more than 140 victims in a single town there — Sarpol-e Zahab, located about 10 miles from the Iraq border. The main hospital in the town was also reported to have been heavily damaged.

"I tried to get back to pick some stuff but it totally collapsed in the second wave," Reza Mohammadi, 51, of Sarpol-e-Zahab, was quoted by The Associated Press as saying. He said he rushed out after the initial quake.

The quake hit around 9:48 p.m. local time Sunday; for hours, rescue and relief efforts were complicated by darkness in the mountainous region. Electrical and water services were also severed in areas near the epicenter.

Iran's seismological center says it has recorded about 118 aftershocks. IRNA says, "the fear of aftershocks kept thousands of people on the streets and in the parks in cold weather."

The head of Iran's Red Crescent said more than 70,000 people need emergency shelter, according to Reuters.

The AP, quoting Iran's state-run IRNA news agency, said rescue work was continuing overnight and would intensify come daybreak. AP quoted the semi-official ILNA news agency as saying at least 14 provinces in Iran had been affected by the earthquake.

Social media from Iran showed signs of damage — broken glass and collapsed structures.

NPR's Jane Arraf, reporting from the northern Iraqi city of Irbil, says dozens of people have been admitted for treatment at the hospital in that city. "Buildings were shaking here," she says. "A lot of people rushed out of their houses into the street."

She says that engineers were checking for damage to the Darbandikhan dam and have informed people living near the river to leave. Officials at the larger Mosul dam said there were no immediate signs of damage.

The U.S. Geological Survey said the epicenter of the quake was located about 150 miles northeast of Baghdad and 450 miles west of Tehran. Tremors could be felt in both capitals, reports said.

"While commonly plotted as points on maps, earthquakes of this size are more appropriately described as slip over a larger fault area," the U.S. agency says.

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