GLOBAL MARKETS-Stocks, oil tumble as grim China PMI sparks growth fears

* Nikkei down 2.0 pct, Asia-Pacific index down 2.1 pct

* China August PMI shrinks at fastest pace in almost 6 1/2 years

* Dollar extends losses as safe-haven U.S. debt yields fall

* Gold, Treasuries up on safe-haven bid

By Shinichi Saoshiro and Nichola Saminather

TOKYO/SINGAPORE, Aug 21 (Reuters) - Global stocks tumbled on Friday after a survey showed Chinese factories contracted at their fastest pace since the depth of the global financial crisis in 2009, sending investors scurrying to the safety of bonds and gold.

Oil prices and emerging market assets also took a hammering, as fears of a China-led deceleration in global growth gripped markets.

MSCI's broadest index of Asia-Pacific shares outside Japan was down 2.1 percent to its lowest since July 27, 2012.

Markets in countries whose economic fortunes were closely linked to China's growth tumbled. Japan's Nikkei lost 2 percent and South Korea's Kospi shed 2.2 percent.

The mood in markets, already soured by overnight weakness on Wall Street, darkened further on a grim reading of China's factory activity.

The Caixin/Markit manufacturing index showed activity in China's factory sector shrank at its fastest pace in almost 6 1/2 years in August as domestic and export demand dwindled. That, coming on the heels of weaker-than-expected data in July, stoked fears of a slowdown in the world's second-biggest economy.

"Markets are pricing in the worst right now," said Herald Van Der Linde, head of Asian equity strategy at HSBC. Particularly with uncertainty about the Chinese currency, "people are saying this is risk, and we step away from the market."

Shanghai stocks fell 1 percent to below the 200-day moving average for the first time since July 2014. That brought losses for the week to 7.9 and pushed the S&P 500 to a six-month low overnight. The Hang Seng index in Hong Kong was down 1.9 percent.

The MSCI emerging markets index slid 1.5 percent to a six-year low.

U.S. stock futures fell more than 0.4 percent to a six-month low in Asian trade after the Chinese PMI was released. The Australian dollar, considered a liquid proxy for China demand, extended earlier losses, falling 0.4 percent to 73.05 U.S. cents.

The market ructions sent gold up to its highest level in more than a month.

The safe-haven U.S. Treasury yields also pulled further down. Yields were already feeling a downward pull after minutes from the Federal Reserve's July meeting offered little clue of a near-term rate hike, denting expectations of a tightening in September.

"The U.S. markets have held up well of late, being viewed as somewhat of a safe-haven. This view seems to have deteriorated somewhat with the S&P 500 closing below its multi-month trading range - a fate the credit markets and the U.S. yield curve have been screaming for some time," wrote Chris Weston, chief market strategist at IG in Melbourne.

Lower Treasury yields in turn weighed on the dollar. The U.S. currency traded near a three-week low of 123.25 yen after sinking from an overnight high of 124.16.

The euro hovered near a two-month high of $1.1250 after surging 1.1 percent on Thursday.

In addition to China worries, emerging markets felt extra tremors after Turkey's lira plunged to a record low against the dollar on Thursday after coalition talks that had been running for months collapsed.