A number of tankers have gathered around Malta storing oil until prices recover.

Shallow water, mild weather and its sheltered location have made Malta a haven for tankers hired by oil and gas firms to exploit the market structure caused by the biggest fall in global oil demand in about 20 years, amid economic slowdown.

About six crude oil tankers, 20 oil product tankers and four liquefied natural gas(LNG) tankers are floating off Malta, the highest density of anchored tankers outside ports in the world, according to AISLive ship tracking data on Reuters.

That means at least 20 million barrels of oil, or about a quarter of the world's daily demand, are on the seas around Malta, while the data showed few in May.

"The ships have to float somewhere where they can get supplies etc, and they have to shelter somewhere," said one oil trader, whose company has stored some oil in tankers.

"The conditions sound good to me for anchoring. It has nothing to do with Malta."

Global oversupply has pulled down prompt oil prices to deep discounts to longer-dated contracts this year, or a market structure called contango, causing oil traders to store oil on land and at sea to make profit by selling later. The trading play has piled up more than 110 million barrels of oil at sea across the globe, with most of them floating in Europe.

Daily world oil consumption is about 83 million barrels. More ships, including crude tankers, are likely to arrive to seek shelter off Malta for a relatively long period of time until winter heating demand picks up and draws some oil from the tankers, traders said.

Earlier this mornth JPMorgan Chase & Co said it had hired hired a crude tanker vessel to store gas oil off Malta's coast..

One shipping source said the vessel, Front Queen, was a new very large crude carrier (VLCC) which had never had a cargo on board meaning that its tanks were clean and able to carry refined products.

The tanker can carry up to 2 million barrels of oil, the source said.