(Updates prices) By Manolo Serapio Jr MANILA, April 18 (Reuters) - London aluminium futures rose to their strongest level since 2011 on Wednesday amid growing worries over tighter supply, while nickel surged more than 4 percent to a three-year peak. U.S. sanctions on major aluminium producer Rusal have pushed aluminium prices by more than 20 percent since the sanctions began earlier this month. Some traders and analysts were puzzled about the sudden spike in nickel prices, with some attributing it to technical factors. Global miner Rio Tinto said adjustments may be made to its 2018 aluminium output following sanctions on its Russian partner UC Rusal imposed by the United States earlier this month. "The sanctions against Rusal and resulting dissociation with Rusal by its banks, suppliers, customers and related parties resulted in heightened concern about a global supply shortage," said Helen Lau, analyst at Argonaut Securities. Three-month aluminium on the London Metal Exchange climbed as high as $2,458 a tonne, its strongest since September 2011, and was trading at $2,449.50 by 0738 GMT, up 1.9 percent. There was little impact on base metals prices from China's surprise move to cut banks' reserve requirement ratio (RRR), which only lifted Chinese steel, coke and coking coal futures sharply. "The RRR cut was positive, but it may not have very significant impact on financial markets. In terms of size, the steel market is also much bigger than base metals," said CRU analyst Wan Ling. China's central bank unexpectedly said it will reduce the cash banks hold as reserves by 100 basis points from April 25. But the move falls short of broad monetary easing, with the authority attaching requirements on how funds must be used. SHANGHAI ALUMINIUM: On the Shanghai Futures Exchange, the most-traded June aluminium contract closed 0.5 percent higher at 14,930 yuan ($2,376) a tonne, just below a nearly three-month high reached on Tuesday. LME NICKEL: Nickel was the day's outperformer, surging almost 5 percent at one stage to hit $14,870 a tonne, the highest since February 2015. It was last up 4.2 percent at $14,805. RIO TINTO: Rio last week declared force majeure on some customer contracts in light of the sanctions on Rusal, the world's second biggest aluminium producer, and said it is reviewing Rusal's 20 percent stake in its Queensland Alumina refinery. RUSAL HALTS ORDERS: Rusal has stopped placing orders with two logistics firms that ship its exports, in a sign of deepening problems for the company. JAPAN TRADERS: Major Japanese trading houses have asked Rusal to stop shipping refined aluminium and other products and are scrambling to secure metal elsewhere, industry sources said. ALUMINA: Prices of alumina, the raw material for making aluminium, have surged after Rio Tinto said it could not fulfil supply contracts because of the sanctions on Rusal. CHINA RRR CUT: The People's Bank of China said banks must use most of the freed-up liquidity to pay back relatively costly loans obtained via the central bank's medium-term lending facility. ALUMINIUM SHEET: The U.S. Commerce Department said it has made a preliminary determination that aluminium sheet imports from China are being subsidized. NORNICKEL: Russia's Norilsk Nickel, or Nornickel, is in talks with battery makers over possible investment in its mining assets, but is also interested in downstream joint ventures in return, a company executive said. INDONESIA EXPORTS: Indonesia exported 8,637,595 tonnes of nickel ore up to March 31, 2018 since its ore export policy was revised in January, 2017, government data showed. COPPER: Benchmark LME copper rose 0.8 percent to $6,933.50 a tonne. In Shanghai, copper gained 0.6 percent to end at 51,170 yuan. MARKETS: Asian shares edged higher, tracking gains on Wall Street, with Chinese equities ending firmer after Beijing boosted liquidity in the banking system. The dollar edged up. 0738 GMT Three month LME copper 6933.5 Most active ShFE 51170 copper Three month LME 2449.5 aluminium Most active ShFE 14930 aluminium Three month LME zinc 3181.5 Most active ShFE zinc 23895 Three month LME lead 2364.5 Most active ShFE lead 18170 Three month LME 14805 nickel Most active ShFE 104750 nickel Three month LME tin 21370 Most active ShFE tin 145690 LME/SHFE COPPER LMESHFCUc3 412.26 LME/SHFE ALUMINIUM LMESHFALc3 -2924.29 LME/SHFE ZINC LMESHFZNc3 100.88 LME/SHFE LEAD LMESHFPBc3 20.6 LME/SHFE NICKEL LMESHFNIc3 -5649.89 ($1 = 6.2833 Chinese yuan) (Reporting by Manolo Serapio Jr.; editing by Vyas Mohan and Gopakumar Warrier)