At least five people are dead after a magnitude 8.2 earthquake struck in the Pacific Ocean off Chile, triggering a tsunami that generated two-metre waves.

The earthquake hit shortly before 9:00pm (local time) at a relatively shallow depth of 10 kilometres and was centred 86 kilometres north-west of Iquique in northern Chile.

The first waves struck Chile's northern coast within 45 minutes of the quake, with roads left gridlocked as residents abandoned their coastal homes for higher ground.

Geophysicist Brian Shiro with the Pacific Tsunami Warning Centre described the resulting tsunami as "fairly big".

"The rule of thumb to issue a tsunami in the first place is one metre. So this is more than twice that," he said.

Interior minister Rodrigo Penalillo says the victims were four men and a woman who died in the cities of Iquique and Alto Hospicio, either of a heart attack or after being crushed by debris.

Sorry, this video has expired Chileans upload footage from earthquake to YouTube

President Michelle Bachelet has declared parts of northern Chile to be disaster zones, including the regions of Arica, Parinacota and Tarapaca.

"The country has faced these first emergency hours very well," she said.

She is expected to visit the region in the coming hours, when daylight will reveal the full extent of the damage.

The president has ordered military be sent to affected areas to prevent looting and disorder, but already a government minister has said 300 female inmates have escaped from a prison.

Authorities say a number of those prisoners have been recaptured.

Landslides, blackouts and fires have also been reported.

Hundreds of thousands heed evacuation warning

Shortly after the earthquake struck, tsunami warning sirens blared along Chile's coastline, urging people to head to higher ground.

Hundreds of thousands heeded the call, evacuating their homes and grid-locking roads with heavy congestion.

Freelance journalist Tom Asapati told the ABC from Santiago that authorities wasted no time issuing the warning.

Sorry, this video has expired Leticia Escamilla from the Red Cross discusses the evacuation in Chile.

"People have moved out of the danger areas as quickly as they can and now they're waiting for the authorities to give the all-clear so they can go back to their homes," he said.

Coordinator with the Chilean Red Cross Leticia Escamilla said evacuations were relatively calm.

"People who have experienced past earthquakes ... have reported feeling more prepared and have shown actions where they are more prepared," she said.

"This is a very seismic country, so people are always kind of alert. People do seem more prepared and knowing what to do this time around."

Hostel owner Kurt Hertramph said guests at his Arica hostel evacuated to higher ground.

"Everybody's gone, everybody's gone. Mostly they are Dutch, and there is a couple from Australia," he said.

"Everybody's out in the hills in this moment. We got an evacuation plan for that. It's running good at the moment and the police are in the area."

Northern Chile has felt a number of aftershocks since the massive earthquake struck.

Kevin McCue from the Australian Seismological Centre says the aftershocks could go on for months and could be as strong as magnitude 7.

Earthquakes are a common occurrence in Chile. In 2010 an 8.8-magnitude earthquake killed more than 300 people.

Fact file: Earthquakes and tsunamis About 80 per cent of tsunamis are caused by an earthquake at or below the sea floor.

About 80 per cent of tsunamis are caused by an earthquake at or below the sea floor. Earthquake causes a large area of the sea floor to either lift up or drop down.

Earthquake causes a large area of the sea floor to either lift up or drop down. The ocean water above the displaced sea floor then rises or falls abruptly. This results in a tsunami wave on the surface of the ocean which travels out in all directions.

The ocean water above the displaced sea floor then rises or falls abruptly. This results in a tsunami wave on the surface of the ocean which travels out in all directions. The upthrust or downthrust of the ocean bottom can occur over hundreds of square kilometres. This pushes up the water above creating a huge mass of water like a hill.

The upthrust or downthrust of the ocean bottom can occur over hundreds of square kilometres. This pushes up the water above creating a huge mass of water like a hill. As the wave approaches shallow water the front of the wave slows down. The height of the water behind increases as it tries to catch up and leads to the wave breaking. Source: ABC Science