chile evacuation
© Javiera Mora Araya/EPAEvacuation under way in Antofagasta, Chile, after an offshore earthquake triggered a tsunami alert

An earthquake of magnitude 8.2 has jolted northern Chile, triggering a tsunami alert and the evacuation of thousands of people from coastal areas. At least five people were killed and more than 300 women escaped from a coastal prison.

The quake was centred under the Pacific Ocean 61 miles north-west of the city of Iquique and struck at 8.46pm as thousands of residents were arriving home from work.

As sirens blared and emergency warnings urged residents to evacuate by foot to higher ground, in coastal cities traffic jams ensued as panicked residents sought to escape the coast. The first tsunami surge measured 2.5 metres (8.2ft) and flooded low-lying areas of Iquique including a medical clinic and bus terminal.

While thousands of residents sought refuge in the hills, an ad-hoc security force of police and members of the Chilean armed forces searched Iquique for the estimated 329 female prisoners thought to have escaped. Initial reports from Chilean investigative police said 16 prisoners had been apprehended. Firefighters, meanwhile, battled a huge blaze in central Iquique and the lack of water and electricity added to a sense of chaos.

In Santiago, a contingent of special forces police boarded a Hercules transport plane and were flown north to provide reinforcements and help prevent looting. In Iquique, police took control of service stations and provided perimeter security for supermarkets. Government officials said attempts to loot stores and abandoned homes in Iquique were rebuffed by police.

Reports of damage to infrastructure and homes began filtering in during the early hours of Wednesday. Several highways were reportedly blocked by rockslides and the airport control tower in Iquique had been damaged.

Strong aftershocks shook northern Chile every few minutes throughout early Wednesday, some measuring above magnitude six. Earthquake experts at the Universidad de Chile predicted the aftershocks would continue for months.

The Chilean president, Michelle Bachelet, called on residents to maintain calm and said a full damage estimate would be made at daybreak. Bachelet immediately announced a visit to northern Chile and confirmed that Brazil, Peru and Argentina had offered material support.

Bachelet, who took office in mid-March, sought to avoid a repeat of her widely criticised reaction to a deadly earthquake during a previous stint as president. An 8.8 earthquake off the coast of Chile on 27 February 2010 killed an estimated 500 Chileans and caused a massive tsunami that government officials had told coastal residents would not happen.

When the huge wave hit - measuring up to 60ft high - it destroyed large swaths of the Chilean coastline and blemished Bachelet's previously stellar reputation.

Over the past four years, the Chilean government has repeatedly held tsunami practice drills and earthquake of magnitude 6.7 on 16 March prompted the evacuation of more than 100,000 people in Iquique. Dozens of small tremors in recent weeks have kept northern Chile residents on edge.

Given that three of the 10 largest earthquakes ever recorded have been in Chile, the populace is long accustomed to earthquake survival protocols. Building standards in Chile require multiple storey buildings to be capable of withstanding a 9.0 earthquake, though in rural areas many older buildings - often made of adobe - are prone to sudden and often deadly collapse.