The UN's highest court has handed Peru a wedge of sea under Chilean sovereignty, redrawing the border at the heart of an over 100-year-old maritime dispute.

The Hague-based International Court of Justice confirmed Chile's sovereignty over waters up to 80 nautical miles (92 land miles, 148 kilometres) from the coast but handed Peru a large swathe of fish-rich ocean beyond that limit.

After six years of legal wrangling, ICJ judges changed the boundaries that Chile had claimed since the early 1950s, in what they described as an "equitable" solution to a dispute dating back to the 1879 War of the Pacific.

Peru dragged Chile to court in 2008, saying their border in the Pacific Ocean was unclear and accusing Chile of appropriating its territory.

Peru claimed sovereignty over a 15,000 sq.m fish-rich patch of the Pacific controlled by Chile, as well as 10,000 sq.m that Chile classifies as "high seas".

The head of Chile's delegation Albert van Klaveren Stork said it "deeply regretted" the ICJ's ruling.

"We deeply regret this decision, which in our opinion is unfounded," he told journalists shortly after the ruling.

Both Chilean and Peru's presidents said earlier their countries would respect the judgments.

Judges drew a line from a point 80 nautical miles off Chile's northern border running southwest into the Pacific until it reached almost 200 nautical miles of Chile's coast, handing Peru the part of the ocean north of the line.

"The court has defined the course of the maritime boundary between the parties without determining the precise geographical coordinates," Judge Peter Tomka told delegates representing the two South American neighbours, calling the decision an "equitable solution".

Peru and Chile have had strained relations stemming from the border dispute.

The 19th-Century War of the Pacific redefined the two countries' borders, with Peru losing 25% of its territory and Bolivia losing access to the sea.