At least 341 people were killed and nearly 6,000 injured when a 7.3-magnitude earthquake shook the mountainous Iran-Iraq border triggering landslides that were hindering rescue efforts, officials said Monday.
The quake could be felt across Iraq, shaking buildings and homes from Erbil to Baghdad and as far west as Anbar province.
In Iraq, local media have reported that six people have died and dozens have been injured in Iraq's northeastern province, closest to the epicentre of the quake.
Iranian state TV said more than 50 people had been injured in Sulaymaniyah province and about 150 in the town of Khanaqin.
In a statement released late Sunday night, Iraq's prime minister Haider al-Abadi issued a directive for the country's civil defence teams and "related institutions" to respond to the natural disaster.
Quake felt as far as the Mediterranean coast
The magnitude 7.3 quake was centred 31 kilometres outside the eastern Iraqi city of Halabja, according to the most recent measurements from the US Geological Survey. It struck at a depth of 23.2 kilometres, a shallow depth that can have broader damage. Magnitude 7 earthquakes on their own are capable of widespread, heavy damage.
The quake was felt as far west as the Mediterranean coast. Its worst damage appeared to be in Iran's western Kermanshah province, which sits in the Zagros Mountains that divide Iran and Iraq. Residents in the rural area rely mainly on farming to make a living.
Iranian social media and news agencies showed images and videos of people fleeing their homes into the night. Some 50 aftershocks followed.
Iran's state-run IRNA news agency reported the increase in casualties early on Monday and said rescue work was continuing overnight and would accelerate during the daytime.
Iran's Supreme Leader Ayatollah Ali Khamenei offered his condolences on Monday morning and urged rescuers and all government agencies to do all they could to help those affected, state media reported.
The semi-official ILNA news agency said at least 14 provinces in Iran had been affected by the earthquake.
Officials announced that schools in Kermanshah and Ilam provinces would be closed on Monday because of the tremor.
Iran sits on major faultlines
Iran sits on many major fault lines and is prone to near-daily quakes. In 2003, a magnitude 6.6 earthquake flattened the historic city of Bam, killing 26,000 people. The last major casualty earthquake in Iran struck in East Azerbaijan province in August 2012, killing over 300 people.
"We are in the process of setting up three emergency relief camps," said Mojtaba Nikkerdar, the deputy governor of Iran's Kermanshah province.
Iran's emergency services chief Pir Hossein Koolivand said it was "difficult to send rescue teams to the villages because the roads have been cut off... there have been landslides."
The worst-hit towns in Iran were Qasr-e Shirin in Kermanshah and Azgaleh, about 40 kilometres northwest, IRNA said.
It added that 30 Red Cross teams had been sent to the quake zone, parts of which had experienced power cuts.
Residents flee homes in Turkey
The quake was felt for about 20 seconds in Baghdad, and for longer in other provinces of Iraq, AFP journalists said.
On the Iranian side of the border, the tremor shook several cities in the west of the country including Tabriz.
It was also felt in southeastern Turkey, "from Malatya to Van", an AFP correspondent said. In the town of Diyarbakir, residents were reported to have fled their homes.
The quake struck along a 1,500 kilometre fault line between the Arabian and Eurasian tectonic plates, a belt extending through western Iran and into northeastern Iraq.