The epicentre of Tuesday's 7.8 magnitude quake lay in southeast Iran but all 40 deaths reported so far have been in Balochistan, where hundreds of mud-built homes suffered damage.
The powerful tremor shook the ground and caused panic as far afield as Kuwait and the Indian capital New Delhi. Thousands of people evacuated towering residential and office buildings in Dubai.
A new aftershock early Wednesday frayed nerves on the Iran-Pakistan border. The US Geological Survey measured its magnitude at 5.7.
In Pakistan, officials said that regular army and paramilitary forces had deployed to help the relief effort after Tuesday's quake brought down homes in the Mashkail area of Balochistan.
Military helicopters carrying medical teams have been sent to the area while paramilitary troops are supplementing the relief efforts, they said.
"The death toll is estimated at more than 40, including women and children," Major Attiq Minhas of the paramilitary Frontier Corps Baluchistan told AFP at Dalbandin airport, around 250 kilometres from Mashkail.
He said 650 personnel were involved in the rescue operation in Mashkail town and that so far medical staff had received 23 wounded people.
Abdul Bari, a 32-year-old tailor who broke his leg, told AFP that his wife and children were fine, but feared that dozens of people from his neighbourhood had been killed or wounded.
"I was on my way home from my tailoring shop when the earth started shaking and soon found myself on the ground with the wall of a house on me," he told AFP in Dalbandin, after travelling for five and a half hours by taxi for help.
"When I felt the tremors, I saw within seconds houses razed to the ground. It was like doomsday," he said, while waiting for an army helicopter ambulance.
"I saw three small children taken out from the debris of a collapsed wall by local people. Two were slightly injured while one seemed serious," he added.
UN chief Ban Ki-moon also expressed condolences after Tuesday's disaster and said the "United Nations stands ready to help as necessary if asked to do so".
The quake struck in the afternoon with its epicentre around 80 kilometres east of the city of Khash, in the Iranian province of Sistan Balochistan, the USGS said.
A local health official in Iran told the Fars news agency that more than 20 villages were probably "severely damaged", based on initial reports.
At least 27 people were hurt in Iran, according to a local governor speaking to the IRNA news agency, but there was no immediate confirmation of any deaths.
The quake came a week after another struck near Iran's Gulf port city of Bushehr, killing at least 30 people.
The International Atomic Energy Agency reported that the latest quake had caused no damage to Iran's nuclear power plant at Bushehr or any other nuclear facilities.
David Rothery, who chairs the volcanoes, earthquakes and tsunamis course at Britain's Open University, said the depth of Tuesday's quake - 82 kilometres underground - would have lessened its impact.
But he added that the area "is mountainous, and damage can be expected from landslides as well as because of poorly constructed buildings".
COMMENTS (10)
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@cautious: go and read the piece by respected journalist Webster about US misadventure and games it play... it will change your mindset if you have any sense of justice and reasoning
And here comes the grant to fill the empty stomach of army officers. We urge US to please distribute the aid yourself, we have no trust in the authorities of Pakistan. Minatwar
@Voice of D.I.Khan
Rubbish. Your corrupt leaders have weakened you - not US Aid. Further - if you don't need or want aid all you have to do is say "thank you - but no" rather than cash the check and then complain which is std Pakistani behavior - hypocritical and rude.
Dying to help the Iranians - please remove the sanctions that even stops the medicines for Irani patients.
Mother Earth is tired and seething. Population boom / industrialisation / global warming has reached its zenith. No time to kill people one by one when they age. This is Her way of revolting.
Never felt anything like this in my life before and I hope I don't have to ever again - thank God we are all safe.
Please Don't let the Americans do their spying on Iran from Pak-Iran border.
Best time to protect Pakistan N assets from HAARP offensive. This one was aimed for Chagai Hills where N test was done and have tunnels bored inside mountain, in some cases 1 mile or 2 miles deep, possibly for secured storage. With this kind of quake, these tunnels can be made to collapse. Same type quake was done a week back near Bushehr N power plant to damage it.
US has weakened us a lot in the name of Aid....
The tremor was felt at my office as well, my desk and computer was shaking for atleast 4 minutes or so. At first I was confused, and then I realized it's an earth quake. I have never experienced such a thing in my life before as I have shifted to Karachi just recently, it was scary.