IQUIQUE, Chile (AFP) - Thousands of Chileans returned home on Wednesday after spending the night on hills following a powerful 8.2-magnitude earthquake that killed six people and sparked tsunami fears as far as Japan.

Police and soldiers patrolled the streets to prevent looting after Tuesday's quake in the north of Chile, which escaped a major catastrophe after nearly one million people evacuated their homes along the lengthy coast.

The chaos - and a collapsed wall - allowed some 300 inmates to escape a women's prison in Iquique, the city closest to the huge quake's epicenter.

Authorities said 110 of them had been recaptured.

The earthquake caused copper prices to jump to a three-week high in the major mining country. The state-run Codelco mining company, the world's top copper producer, evacuated some facilities on the coast but none suffered damage.

No houses collapsed, but roofs sagged, windows broke and products tumbled from shelves at shopping centers in Iquique, located about 1,800 kilometers north of the capital Santiago.

Some 2,500 homes were damaged in the town of Alto Hospicio, near Iquique, the National Emergency Office said.

Thousands of people slept in the open on high ground surrounding the city during the night. They returned home after authorities lifted the tsunami alert 10 hours later.

People stood in long lines to get fuel at service stations, with gasoline rationed to a maximum of $20.

The sea rushed 200 metres inland, flooding some streets, authorities said. Fishermen reported that 80 boats had been destroyed, sunk or floated out to sea.

Iquique's airport control tower was damaged and flights there, to Arica and the northern city of Antofagasta were canceled, though they resumed on Wednesday.

Landslides covered the road linking Iquique with the rest of the country.

Six people - five men, including a Peruvian, and one woman - were killed in Iquique and the nearby Alto Hospicio municipality.

Another nine people were injured in neighbouring Peru, where homes were damaged.

In Arica, near the border with Peru, people fearing aftershocks stood in huge lines outside stores to buy food, batteries and flashlights after the power went out.

"The earthquake was terrible. Now we are bracing for a mega-earthquake," said Jorge Reyes, a consultant for a US mining company who lives in Arica.

Like Iquique, the city avoided major damage, though walls were cracked in older homes.

The tremors were felt as far inland as landlocked Bolivia and sparked evacuation warnings up the Pacific coast of South America and into Central America.

The earthquake produced a mini tsunami across the Pacific, with waves of 20 centimetres reported in the Japanese city of Kuji.

The Japanese Meteorological Agency had issued a tsunami advisory, warning of potential waves of up to one metre and urging people to "get out of the water and leave the coast immediately."

Chile's President Michelle Bachelet declared disaster zones in the north and toured the area to survey the damage and lead relief efforts.

She deployed troops to prevent looting and disorder from breaking out, as they did after a deadly 8.8-magnitude quake in 2010.

More than 500 people died and $30 billion in damage was wrought in that disaster after Bachelet's government prematurely called off a tsunami alert, causing people to return home only to die in the ensuing waves.

This time, however, the evacuations appeared to have gone smoothly, with officials saying lessons were learned from past disasters.

"A titanic task was dealt with in an exemplary way," Bachelet said.

The quake struck at 8:46 pm (2346 GMT) at a depth of 10 kilometers, 83 kilometers from Iquique, the United States Geological Survey said. Chilean seismologists said it was four times deeper.

At least 20 aftershocks rattled Chile, and authorities warned that more may come in the next few days.