Update 9.31am: More than 300 people are known to have died and 2,500 are injured after the earthquake, according to officials in Iran.
It has shaken the Iraqi border region where the coroner's office has warned the figures will increase.
More than 1,000 aftershocks have been recorded.
Earlier:More than 200 people have been killed and 1,686 injured in an earthquake along the Iran-Iraq border, Iranian state TV has said.
The Baghdad government did not immediately give word on casualties in that country, although Prime Minister Haider al-Abadi issued a directive for the country's civil defence teams and "related institutions" to respond to the natural disaster.
The magnitude 7.3 quake was centred 19 miles outside the eastern Iraqi city of Halabja, according to the most recent measurements from the US Geological Survey.
It struck at a depth of 14.4 miles, a shallow depth that can have broader damage. Magnitude 7 earthquakes on their own are capable of widespread, heavy damage.
The earthquake 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 television reported the increase in casualties - to a total of 207 - earlythis morning and said rescue work was continuing overnight and would accelerate during the daytime.
Iran's Supreme Leader Ayatollah Ali Khamenei offered his condolences this 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 today because of the temblor.
Iranian state TV also said Iraqi officials reported at least six people dead inside Iraq, along with more than 50 people injured in Sulaymaniyah province and about 150 in the town of Khanaquin.
Iran sits on many major fault lines and is prone to earthquakes. 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 more than 300 people.