In Muscat, the tremors, which were felt around 2.45pm prompted people to rush out of buildings on to the streets.
Iran's seismological centre said the 7.5 magnitude earthquake was centered near Saravan, a sparsely populated area about 48km from the Pakistani border. The US Geological Survey put the preliminary magnitude at 7.8 and at a depth of 15.2km.
The quake struck less than a week after a 6.1 magnitude quake hit near Bushehr, on Iran's Gulf coast, killing at least 37 people.
A resident in the quake zone, Manouchehr Karimi, said that 'the quake period was long' and occurred 'when many people were at home to take a midday nap'.
Pakistani news channels showed buildings shaking in the southern city of Karachi, where people in panic came out from offices and homes.
There was no immediate word on any damage and people were seen standing outside their homes and offices even minutes after the quack rattled various parts of the country.
In 2003, some 26,000 people were killed by a magnitude 6.6 quake that flattened the historic southeastern Iranian city of Bam.
Story abroad: http://www.editor.muscatdaily.com/Archive/Gcc/Huge-quake-hits-Iran-kills-34-in-Pakistan-26sr
(With inputs from Agencies)