LONDON, June 12 (Reuters) - Russian aluminium stocks in warehouses registered with the London Metal Exchange (LME) jumped to 68% of the total in May, from 52% in April, data on the exchange's website showed on Monday.

The world's oldest exchange and largest market for industrial metals has not banned Russian metals from being traded and stored in its system since Moscow invaded Ukraine, as there are no Western sanctions on Russian base metals.

However, the LME said that "Russian aluminium continues to flow through its network, and that a meaningful set of global consumers continue to accept Russian metal". The LME will continue to monitor the data, it added.

Large amounts of Russian aluminium in LME warehouses is a concern for the industry as it could distort pricing on the exchange used as a benchmark for contracts to buy and sell between producers, consumers and traders.

In LME warehouses in May there was a total of 263,125 tonnes of Russian aluminium, a metal is used widely in the transport, construction and packaging industries, the data showed.

Of the 57,925 tonnes of primary aluminium warranted in May, 67% was Russian and 33% non-Russian, the LME said.

A warrant is an ownership document for metal in LME-registered warehouses. Cancelling warrants indicates an intention to take delivery of metal from the warehouses unless it is rewarranted.

Of the 167,550 tonnes of primary aluminium warrants cancelled, 19% was Russian and 81% non-Russian in May, the LME said, adding that most of this cancelled stock remains in the warehouse.

Of the 45,300 tonnes of primary aluminium loaded-out last month, 54% was Russian and 46% non-Russian, it added.

The LME report also showed that as of May 31, the share of Russian copper stocks fell to 33% from 36% in April, or 29,600 tonnes, while nickel was stable at 20%, or 7,224 tonnes. (Reporting by Polina Devitt; editing by Jason Neely and Conor Humphries)