People sit on the rubble of a destroyed house after an earthquake in the city of Darbandikhan, northern Iraq, Monday. Authorities reported that a powerful 7.3 magnitude earthquake struck the Iraq-Iran border region on Monday and killed more than 400 people in both countries.

TEHRAN, Iran — Rescuers dug with their bare hands Monday through the debris of buildings brought down by a powerful earthquake that killed more than 400 people in the once-contested mountainous border region between Iraq and Iran, with nearly all of the victims in an area rebuilt since the end of the ruinous 1980s war.

Sunday night’s magnitude 7.3 earthquake struck about 19 miles outside the eastern Iraqi city of Halabja, according to the most recent measurements from the U.S. Geological Survey. It hit at 9:48 p.m. Iran time, just as people were going to bed.

The worst damage appeared to be in the Kurdish town of Sarpol-e-Zahab in the western Iranian province of Kermanshah, which sits in the Zagros Mountains that divide Iran and Iraq.

Residents fled into the streets as the quake struck, without time to grab their possessions, as apartment complexes collapsed into rubble. Outside walls of some complexes were sheared off by the quake, power and water lines were severed, and telephone service was disrupted.

Residents dug frantically through wrecked buildings for survivors as they wailed. Firefighters from Tehran joined other rescuers in the desperate search, using dogs to inspect the rubble.

The hospital in Sarpol-e-Zahab was heavily damaged, and the army set up field hospitals, although many of the injured were moved to other cities, including Tehran.

It also damaged an army garrison and buildings in the border city and killed an unspecified number of soldiers, according to reports.

Iran’s Supreme Leader Ayatollah Ali Khamenei immediately dispatched all government and military forces to aid those affected.

Many of the heavily damaged complexes in Sarpol-e-Zahab were part of construction projects under former hard-line President Mahmoud Ahmadinejad. The newly homeless slept outside in the cold, huddled around makeshift fires for warmth, wrapped in blankets — as were the dead.

The quake killed 407 people in Iran and injured 7,156 others, Iran’s crisis management headquarters spokesman Behnam Saeedi told state TV. Most of the injuries were minor, he said, with fewer than 1,000 still hospitalized.

The semi-official Tasnim news agency reported 445 dead and 7,370 injured. There was no immediate explanation of the discrepancy, although double-counting of victims is common during such disasters in Iran.

The official death toll came from provincial forensic authorities based on death certificates issued. Some reports said authorities have warned that unauthorized burials without certification could mean the death toll was actually higher.

In Iraq, the earthquake killed at least seven people and injured 535 others, all in the country’s northern, semiautonomous Kurdish region, according to its Interior Ministry.