A powerful earthquake struck southeast Iran near the border with Pakistan on Tuesday but with communications to the area badly disrupted, officials gave differing assessments of the casualty toll.
One Iranian official said hundreds of people were feared to have been killed. But an Iranian lawmaker from the region said the number of deaths was "not high".
A Pakistani official said at least five people been killed in Pakistan.
Tremors from the 7.8 magnitude quake were also felt as far away as India and Gulf states.
The quake was centered in a remote desert and mountain region which is not densely populated. Assessing the damage was difficult due to the collapse in the communications network.
"It was the biggest earthquake in Iran in 40 years and we are expecting hundreds of dead," an Iranian official, who spoke on condition of anonymity, told Reuters.
But Iranian politician Hamid Reza Pashang told the Mehr news agency: "From what we have heard from people in the stricken areas, we have learned that the number of deaths is not high."
"I have talked to the people of Zabul, Saravan, Khash and other areas hit by the earthquake and they have said, the earthquake was not of a kind to cause many deaths," he said.
It was not clear how he had reached them, given the breakdown in power and communications.
Iranian state television said at least 40 people were killed but acknowledged it had no official confirmation.
People in the city of Zahedan poured into the streets when the earthquake struck, Iran's Fars news agency reported. It also said Saravan city had not suffered serious damage.
The US Geological Survey said the quake hit at 10:44 GMT at a depth of 15.2km (9.4 miles). The epicenter was 201 km (125 miles) southeast of Zahedan and 250km northwest of Turbat in Pakistan, it said.
The Iranian Red Crescent's Mahmoud Mozaffar told state television that rescue and evaluation teams have been sent to to the afflicted area.
Second in a week
It was the second big quake to hit Iran in a week.
On April 9, a powerful 6.3 magnitude quake struck close to Iran's only nuclear power station, killing 37 people, injuring 850 and devastating two villages.
Most of Iran's nuclear-related facilities are located in central Iran or its west, including the Bushehr nuclear power plant on the Gulf coast.
"It is far from Bushehr and other nuclear-related facilities," Iran expert Ali Vaez of the International Crisis Group think tank told Reuters.
"However, the recent tremors are ominous reminders of how earthquake prone Iran's terrain truly is and how critical it is for the iranian government to be prepared for a nuclear emergency," Vaez said.
Iran sits on major geological faultlines and has suffered several devastating earthquakes, including a 6.6 magnitude quake in 2003 that flattened the city of Bam, in Iran's far southeast, killing more than 25,000 people.
This quake also shook tall buildings in New Delhi, sending people running into the streets. People also evacuated buildings in Qatar and Dubai.
"I was working and my work station was shaking," said Viidhu Sekhri, 35, an underwriter at a New Delhi insurance company.
"Then it was a bit shaky so we just rushed outside."
Earlier in the day two smaller tremors were felt in India's Himalayan region close to the Chinese border.
An official at India's disaster management authority said the tremors felt in New Delhi and across northern India were because of the earthquake in Iran.
The Iranian Students News Agency quoted an official at the Emergency Medical Center at the Sistan and Baluchistan Medical University saying three people had been injured.