A million people were evacuated in Chile after an 8.3-magnitude quake struck offshore in the Pacific, killing at least 10 people and triggering tsunami waves along its northern coast.

Wednesday night's earthquake was the sixth most powerful in the history of geologically volatile Chile and the strongest anywhere in the world this year, officials said.

Buildings swayed as far away as in Buenos Aires, Argentina, 1,500 kilometers (1,000 miles) to the east.

In northern Chile, people were evacuated to higher ground as strong aftershocks followed through the night, triggering a tsunami alert for the Chilean coast.

Huge waves of up to 4.5 meters (15 feet) came crashing onshore in the Coquimbo region. The fishing village of Tongoy was among the worst-hit, with television showing entire areas along the seafront completely destroyed.

Two-meter waves also struck the tourist port of Valparaiso, according to the Chilean navy, flattening several beachfront restaurants.

President Michelle Bachelet was traveling to the quake-hit area on Thursday to assess the relief effort.

"We know there can be aftershocks and we are monitoring the situation minute by minute," she said.

The Hawaii-based Pacific Tsunami Warning Center said tsunami waves were also possible in French Polynesia, Hawaii and California, officials said, as well as smaller waves as far afield as Japan and New Zealand.

- 'Ring of fire' -

The north Chilean coastal city of Illapel was among the hardest-hit, with power knocked out, homes collapsing and at least one fatality.

Daybreak revealed the damage to the northern town of 30,000, with shacks destroyed, store shelves overturned and the local cemetery a chaos of broken crosses, vases and coffins.

"It was the most horrific moment, a terrible thing," local resident Ana Cortes, 35, told AFP. "Everything just kept moving, for the longest time."

Chile lies on what is known as the "Ring of Fire" -- an arc of fault lines that circles the Pacific Basin and is prone to frequent earthquakes and volcanic eruptions.

In February 2010, an 8.8-magnitude quake off the Chilean coast killed more than 500 people and inflicted an estimated $30 billion in damages.

Wednesday's quake struck at 2254 GMT, measuring 8.3 on the so-called moment magnitude scale, according to the United States Geological Survey (USGS).

It occurred at a shallow depth, 228 kilometers north of Santiago, a city of 6.6 million people.

The tremor was clearly felt as far as Buenos Aires, where panicked residents were sent running out of apartment blocks.

A precautionary alert for Peru was later called off, but scared residents near the Chilean border remained out on the streets and on higher ground.

In Santiago itself, there were scenes of pandemonium as thousands fled swaying buildings, with similar scenes reported across the coastal north.

Choapa province, closest to the epicenter, was declared a disaster zone.

Interior Minister Burgos revised the death toll upwards from eight to 10 people.

He said evacuations of coastal towns and cities had been ordered as a precautionary measure.

School classes were cancelled in coastal areas, where more than 135,000 families were without power.

"It was a nightmare," Illapel resident Maria Ramirez told AFP as she swept dirt from the door of her house.

"We felt the tremors for a long time, too long. And then all the aftershocks -- it was terrible," she said. "I couldn't stay standing, but luckily we made it out alive."

Facebook said it had activated a geolocation tool allowing people in Chile to reassure friends and loved ones about their well-being.

The Safety Check tool is accessed through Facebook's regular user interface, and lets members check whether their contacts are in a disaster zone, signal their own presence and let others know they are safe and well.