Aid workers on Wednesday were continuing efforts to reach remote victims of an earthquake centered in Iran, which jolted the region on Tuesday,
Despite the epicenter of the 7.8 magnitude quake being in southeast Iran, all 40 deaths reported so far have been across the border in Pakistan's poor province of Baluchistan.
Hundreds of mud-built homes suffered damage, as neighboring Gulf states also felt the tremors.
A new aftershock early Wednesday frayed locals' nerves on the Iran-Pakistan border. The US Geological Survey measured its magnitude at 5.7.
Military helicopters carrying medical teams have been sent to the area while paramilitary troops are supplementing the relief efforts, they said.
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 Baluchistan.
"The death toll is estimated at more than 40, including women and children," Major Attiq Minhasof from the paramilitary Frontier Corps Baluchistan told AFP news agency at Dalbandin airport, around 250 kilometers (155 miles) 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.
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 epicenter around 80 kilometers (50 miles) east of the city of Khash, in the Iranian province of Sistan Baluchistan, 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 earthquake also shook buildings in Abu Dhabi and Dubai, across the waters of the Gulf in the United Arab Emirates. It was also felt in the Saudi capital Riyadh and in Oman.
In the tourist hub of Dubai, residential and office buildings were evacuated and thousands of people gathered outside skyscrapers.
The quake was also strongly felt in Kuwait, particularly in coastal areas, and in the Bahraini capital Manama, where buildings in the central financial district were evacuated.
It was felt across northern India, including in the capital New Delhi. where tremors rattled buildings and led many office workers to run into the street as a precaution.
The quake came a week after another struck near Iran's Gulf port city of Bushehr, killing at least 30 people.