According to the USGS, the quake measured 7.8 on the Richter scale.
A major 7.8 magnitude earthquake struck Iran near the border with Pakistan on Tuesday killing 40 people and injuring many.
An Iranian government official said on Tuesday he expected hundreds of deaths.
"It was the biggest earthquake in Iran in 40 years and we are expecting hundreds of dead," said the official, who spoke on condition of anonymity.
The tremors were also felt in Pakistan, India and other gulf nations.
13 people were killed in southwestern Pakistan on when the region was struck by tremors from the earthquake.
The three women and two children were killed when their mud house collapsed in the district of Panjgur in the Pakistani province of Baluchistan, according to government officials from the area.
The US Geological Survey said the quake hit at 10:44 GMT at a depth of 15.2 km (9.4 miles). The epicentre was in southeast Iran in an area of mountains and desert.
It was located 201 km (125 miles) southeast of the Iranian city of Zahedan and 250 km northwest of Turbat in Pakistan, USGS said.
The epicentre of the quake was 86 km from the city of Khash, near Pakistan's border.
Tremors were felt in the capital and its adjoining areas Tuesday afternoon.
Many people rushed out of their offices and homes in the National Capital Region after the quake that lasted several seconds.
According to the USGS, the quake measured 8 on the Richter scale.
A powerful 6.3 magnitude quake struck close to Iran's only nuclear power station on April 9, killing 37 people and injuring 850 as it destroyed homes and devastated two villages.
Tremors felt in India too
Strong tremors rocked large parts of north India, including the national capital and its adjoining areas, Tuesday evening. There were no immediate reports of any casualties. The quake measured 7.8 on the Richter scale at its epicentre on the Pakistan-Iran border.
"The epicentre of the quake was the Pakistan-Iran border and it measured 7.8 on the Richter scale," V. Dattatreya, head, seismology, India Meteorological Department (IMD), told IANS.
The quake took place at 4.14 p.m. (IST) at a depth of 33 km, an official said.
The strong tremors that lasted several seconds, leading to panic in many places. People rushed out of their offices and homes in the National Capital Region.