* LME zinc, aluminium stocks at multi-year lows
* Asian stock index touches 3-year high, helps metals (Adds official midday prices)
By Maytaal Angel
LONDON, July 22 (Reuters) - Zinc hit a three-year high and aluminium touched a 16-month peak on Tuesday as investors sought more exposure to commodities with tightening supply-demand balances and were encouraged by falling inventories and firm equity markets.
London Metal Exchange stocks of zinc fell by 400 tonnes to 656,275 tonnes, their lowest in 3-1/2 years, while aluminium stocks fell by 9,075 tonnes to 4.938 million tonnes, their lowest in nearly two years. MZN-STOCKS MAL-STOCKS
Investors are slowly being drawn back into commodities, attracted by stronger global economic growth and more volatility within some sectors, typified by current investment flows out of grains into industrial metals.
"There's a certain amount of relative value going on where investors prefer one metal over another," Macquarie analyst Vivian Lloyd said.
She added, however: "In our view it's premature. The real tightness (in zinc) will hit next year, but (right now) it's a market half the size of copper with four times as much stock."
Three-month zinc on the London Metal Exchange rose to $2,373, the highest since August 2011, before trading at $2,369 a tonne in official midday rings, up 1.41 percent for the day. That level brings gains for the year to around 15 percent.
Forecasts for zinc prices have been driven higher this year by a paucity of big mine projects just as existing mines such as Century in Australia dry up.
Also, data on Monday showed China's zinc imports rose 123.55 percent in June year on year to 68,475 tonnes, bringing gains for the year to 38.14 percent.
Helping metals generally, a major index of Asian stocks touched a three-year high on Tuesday, while a Chinese index of the leading Shanghai and Shenzhen A-share listings closed at its highest in three months.
"The combination of stronger growth but less stimulatory monetary policy in the U.S. is more likely to be a net positive for commodity prices - especially industrial metals - than for those of other assets ... provided there are no further shocks from China," Capital Economics said in a note.
China's is the world's largest base metals consumer.
LME aluminium reached as high as $2,044 a tonne, the loftiest since February last year, bringing gains for the year to around 13 percent. It traded at $2,038 a tonne in rings, up 0.89 percent.
The discount for cash aluminium over the three-month price CMAL0-3 has fallen to 18-month lows amid dwindling exchange stocks, reigniting a long debate about how tight the market really is.
Years of aluminium smelter cutbacks due to depressed prices have eroded supply just as global demand recovers, in part due to a revival in the U.S. and European auto sectors.
Still, aluminium stocks remain high overall, with just under 5 million tonnes sitting in LME warehouses, and output in China is on the rise, prompting some analysts to question the sustainability of the rally.
LME copper ticked up by 0.50 percent to $7,060 a tonne, recovering after recent inflows to exchange stocks sparked concern that an expected shift into surplus had begun.
The global world refined copper market showed a 183,000 tonne deficit in April, compared with an 84,000 tonne deficit in March, the International Copper Study Group said in its latest monthly bulletin.
LME lead was last bid up 1 percent in rings at $2,225 a tonne, while tin traded down 0.23 percent at $22,150 a tonne and nickel traded up 0.93 percent at $19,100 a tonne.
Three month LME copper
Most active ShFE copper
Three month LME aluminium
Most active ShFE aluminium
Three month LME zinc
Most active ShFE zinc
Three month LME lead
Most active ShFE lead
Three month LME nickel
Three month LME tin ($1 = 6.2048 Chinese Yuan) (Additional reporting by Melanie Burton; editing by Jane Baird)