Rescue teams are working to dig survivors out of the rubble in the devastated zone north-east of the city of Tabriz.
The quakes, which the USGS put at magnitude 6.4 and 6.3 respectively, struck near the city of Tabriz on Saturday afternoon (local time).
Officials say they came within minutes of each other, followed by aftershocks.
At least 40 aftershocks have prompted thousands of people to flee their homes and remain outdoors.
The head of the regional natural disasters centre, Khalil Saie, called for calm on state television.
"We are asking people to not panic. Help is arriving and rescuers are already at the scene," he said.
Most of the casualties are thought to be in outlying villages.
Officials say at least 60 rescue teams are at work, using seven dog squads to detect buried survivors.
The disaster zone is located around 90 kilometres from the borders with Armenia and Azerbaijan, and around 190 kilometres from the border with Turkey.
The towns of Ahar and Varzaqan, 60 kilometres from Tabriz, were the hardest hit by the quake.
Heris, another town close by, was also badly shaken and scores of villages were decimated.
"Sixty villages have been 60 to 80 per cent destroyed and four villages were 100 percent destroyed," Mr Saei said.
Tehran University's Seismological Centre said the first earthquake hit at 4.53pm (local time), while the second struck 11 minutes later.
A series of smaller aftershocks rating 4.7 or less rapidly followed.
Those hurt have been taken to hospitals in Tabriz and Ardebil, the two biggest nearby cities, both of which escaped relatively unscathed.
Iran's Red Crescent has taken over a sports stadium to shelter the 16,000 people left homeless or too afraid to return indoors.
It also provided 3,000 tents, blankets and tonnes of food - all a sign of years of preparedness in a nation prone to sometimes catastrophic seismic activity.
Iran sits astride several major fault lines and is prone to frequent earthquakes, some of which have been devastating.
The deadliest was a 6.6-magnitude quake which struck the southern city of Bam in December 2003, killing 31,000 people and destroying the city's ancient mud-built citadel.