- The massive magnitude 7.8 earthquake struck at about 10.45am (GMT)
- ABC News described the quake as the strongest in more than half a century.
- Pakistan suffered the worst so far, with at least 30 reported killed.
- More aftershocks were expected.
- Iran's Red Crescent said the country faced a 'complicated emergency situation'.
- The epicentre was in southeast Iran in an area of mountains and desert, 201 km (125 miles) southeast of Zahedan and 250 km northwest of Turbat in Pakistan, USGS said.
A massive earthquake struck the border region of Pakistan and Iran, sending tremors across the Gulf and South Asia. 30 people were reportedly killed in Pakistan, but there was confusion in Iran with some sources initially claiming 40 people died.
Iranian officials played down the claims, saying no deaths had been confirmed in the country following the quake
Pakistan has suffered the most from the quake, with dozens killed and hundreds of homes destroyed. Karachi witnesses said they saw buildings moving and ran out into the open..
The massive magnitude 7.8 earthquake struck at about 10.45am GMT, with a depth of 15.2km (9.4 miles).
It was the second time in a week that the region had been hit by tremors; the last quake struck south-west Iran on April 9 killing 37 people and injuring 850, and devastating infrastructures. It hit very close to Iran's only nuclear power plant.
British newspaper The Guardian likened Tuesday's 7.8 quake to the 2008 Sichuan Province, China, earthquake that killed an estimated 68,000 people.
In the UAE
In Dubai, the streets filled up with people and traffic as skyscrapers were evacuated, including the world's tallest tower, the Burj Khalifa.
As people stood on the streets waiting for some guidance many took to online social forums.
“Loads of buildings in Dubai Media City evacuated after earthquake,” tweeted Ben Flannagan.
“Dubai is shaken by its second earthquake in a week. The epicentre of last week’s was in Iran, this one felt much closer, evacuations underway,” Gary Meenaghan added.
Maysa, who works in Dubai’s Media City, said she ran down 40 floors. "The desks started shaking and there was an evacuation call to action so we came down. It lasted for a couple of seconds, maybe five."
Rozelle who works on the 45th floor of a Dubai Media City tower, said: “I don't know what time it happened. I thought I was dizzy but my colleagues told me that it was shaking.
"When we heard the announcement to evacuate we just ran down the stairs as the lift was full.”
Rest of Gulf
Tremors were felt across the Gulf in Riyadh and Dammam in Saudi Arabia as well as Manama, Bahrain and Qatar.
The BBC Online website quoted Michael Stephens, a researcher at RUSI Qatar, as saying from his office in Doha: "I definitely felt the walls shaking. It lasted for about 25 seconds."