YEREVAN, AUGUST 24, ARMENPRESS. A strong earthquake hit central Italy, leaving terrified residents huddled outside collapsed buildings overnight and an unknown number of people trapped beneath the rubble, CNN reports.

At least 21 people died following the 6.2-magnitude earthquake early Wednesday, according to CNN affiliate Rai.

The earthquake hit 10 kilometers (6.2 miles) southeast of Norcia at 3:36 a.m., the United States Geological Survey said. Its tremors rattled Rome -- about 100 miles away.

In Amatrice, buildings collapsed and left the mountainous town in ruins.

"The town is no more," Mayor Sergio Pirozzi told the affiliate. "I have an appeal to make: we have access roads to the town cut off and people under the rubble, help us."

He said there was no power, and it was crucial for rescue crews to get to the town.

Rescue workers called Amatrice residents' cellphones, and tried to get to those who answered, the affiliate reported. If there was no answer, rescuers moved on to the next person.

While the number of people trapped under the rubble is unknown, rescuers are focusing on finding survivors, said Fabrizio Curcio, head of Italy's civil protection.

"I ask you to be patient in terms of numbers," Curcio told the affiliate.

"We don't have any more light (electricity) and it is urgent to clear the access roads," he said.

Tommaso della Longa, a spokesman for the Red Cross, said the images coming out of Amatrice are grim.

"The picture we got from our delegate in Amatrice are telling us a terrible story of a small city almost completely destroyed," he said. "The situation is difficult at the moment."

The priority is to find survivors, he said.

"These areas are in central Italy and are in middle of mountains and valleys," he said. "There are small houses in the middle of the valley that are completely alone and they need help. It'll take some time to reach them."

Charlotte Smith, coach of Elon University women's basketball team in North Carolina, was in Rome with her players when the quake hit.

"It lasted for at least 30 seconds. The entire hotel was shaking," she said. "I went down to the lobby and there were a lot of people waiting there. ... Then an earthquake happened 30 minutes later."

She said their flight is still on schedule to leave for the United States later Wednesday.

About an hour after the earthquake, a 5.5-magnitude aftershock hit near Norcia, one of several that followed.

"At that shallowness and magnitude of 6.2, we're going to expect lots of aftershocks for next several hours and maybe the next several days," said Jessica Turner of the USGS.

Landslides are likely because the earthquake struck in a mountainous area, she said.

Although the extent of damage and injuries was not immediately clear, the earthquake could be devastating.

The Italian Civil Protection has mobilized three helicopters, six vehicles and a mobile convoy to the affected areas. It plans to set up mobile medical or triage units.

It said the biggest damage appears to be in Amatrice and Accumoli in Lazio region, and the Umbria and Marche regions.