The oil major has booked 90,000 deadweight tonne (dwt) clean petroleum tanker the River Pride for $2.1 million (1.27 million pounds) from June 20, and a second tanker, the Survetta, of similar size from June 30, shipbrokers said.

"Both tankers are going to be used for storage in Northwest Europe, and will likely be loading up product in Asia," a Singapore-based shipbroker said.

"This is the first booking we have seen from them on the open spot market...they have been using their own vessels for storage so far."

Shell could have as many as 10 ships being used to store gas oil or jet fuel in Northwest Europe, traders and shipbrokers said.

"They are extremely secretive on their floating storage, so it's hard to say, but they could have anything from 10 ships...or as high as 15 ships," a London-based shipbroker said.

Last week Shell's outgoing Chief Executive Jeroen van der Veer said he was seeing early signs that Western gasoline and diesel markets were steadying after a slump late last year.

Global diesel storage at sea has risen since April by more than 70 percent to around 41 million barrels, a Reuters survey showed.

The demand for ships to store fuel has boosted freight rates for the Long Range 2 tankers which are mostly being used for this, shipbrokers said. The tankers can hold between 600,000 and 1 million barrels of oil.

FAST

"The rates are moving up fast, tonnage is getting tight and now more people are eying using supertankers for storage of clean product," an Asian-based shipbroker said.

U.S. investment bank JP Morgan Chase has hired a

new crude supertanker to store gas oil off Malta's coast, an unusual sign traders are looking to take advantage of the weaker crude oil freight rates to store distillates.

The Wall Street bank had leased the tanker for 270 days, shipbrokers said.

Independent Russian trader Gunvor and European firm Vitol have also booked supertankers to store gas oil.

"We are expecting to see more traders get in on this, because freight right now is just so cheap," a Singapore-based shipbroker said.

"We could see more banks get into this...why not? Other trading houses are also looking to get in the game."

This discount is key to traders storing oil at sea to make profits by selling it later, also known as contango.

Despite last week's oil price rally and more positive sentiment about demand, distillates remain weak, traders said.

"We have a lot of oil out on the water, yes the worst of the economic slide is over," a Singapore based trader said.

"But you're not going to see demand as it was last year, it's still going to be pretty weak, so how do you move all this oil into the market."

(Editing by Sue Thomas)