An earthquake measured at magnitude 7.2, reportedly the worst in a decade, hit eastern Turkey on Sunday.
At least one seven-story building was reduced to rubble, and other structures were destroyed near the city of Van, CNN reported.
The last quake of that magnitude in Turkey -- a 7.2 tremor in Duzce in 1999 -- killed 894 people, the USGS reported. A 7.6 earthquake in Izmit, Turkey, killed more than 17,000 people the same year, according to the USGS.
Sunday's major quake hit at 1:41 p.m. local time and was followed by at least seven aftershocks, American and Turkish monitoring agencies reported.
Turkish Prime Minister Recep Tayyip Erdogan plans to fly to the region on Sunday afternoon to survey damage.
Officials now believe the quake could have killed as many as 1,000 people, the Los Angeles Times and wire services report. Its effects were felt as far away as Iran. From the Times' report:
Terrified residents spilled into the streets in panic as rescue workers and residents using their bare hands and shovels struggled to evacuate people believed to be trapped under collapsed buildings, television footage showed.
In Van, at least two buildings collapsed, Bekir Kaya, the mayor of Van town, told NTV. One of them was a seven-story building, according to Turkey's state-run Anatolia news agency.
At least 50 people were treated for injuries in the courtyard of the state hospital in Van, said the state-run Anatolia news agency.
"The telephone system is jammed due to panic, and we can't assess the entire damage immediately," Kaya said.