* European shares open firmly in red; Frankfurt leads fallers
* Wall Street futures point to weak open
* Apple's Frankfurt shares down more than 8 pct
* Currency 'flash crash' sends yen soaring
By Josephine Mason and Helen Reid
LONDON, Jan 3 (Reuters) - Apple's rare warning on revenue rocked financial markets on Thursday, as investors sought safety in bonds and less risky assets amid renewed concerns about slowing global economic and corporate growth.
Asian and European shares fell sharply, led by a sell-off in technology stocks, and U.S. equity futures pointed to a weaker open on Wall Street after Apple cut its revenue forecast, its first downgrade in nearly 12 years, blaming weaker iPhone sales in China.
The news also jolted currency markets and German government bond yields held close to their lowest in over two years.
"For the moment, investors have reacted by going into non-risky assets," said Philippe Waechter, chief economist at Ostrum Asset Management, in Paris.
"No one wants to take any risk because none of the uncertainties we are facing have been lifted, whether it's Brexit, this trade war, or growth. Investors are putting their heads in the sand and waiting."
Apples shares tumbled in after-hours trade and those listed in Frankfurt were down 8.6 percent in early European deals.
The news sparked a 'flash crash' in holiday-thinned currency markets as growing concerns about the health of the global economy, particularly in China, sent investors scurrying into the safe-haven of the Japanese yen, which was poised for its biggest daily rise in 20 months.
Apple's warning came after data earlier this week showed a deceleration in factory activity in China and the euro zone, indicating the ongoing trade dispute between the United States and China was taking a toll on global manufacturing.
Major European bourses were firmly in negative territory by midmorning - Frankfurt's DAX, with its exposure to Chinese trade and tech-heavy constituents, was the biggest faller and down as much as 1.2 percent, while Paris' CAC40 dropped 1.1 percent and London eased 0.4 percent.
Chipmakers who supply parts to Apple were the worst hit, sending technology stocks to their lowest since February 2017.
U.S. stock futures pointed to another rough start on Wall Street, with Nasdaq E-minis down 2.7 percent and S&P 500 E-minis off 1.6 percent.
Overnight, shares in China and Hong Kong see-sawed between gains and losses as investors braced for Beijing to roll out fresh support measures for the cooling Chinese economy.
"Chinese authorities have got the luxury of having control not just of the fiscal parts of the government tool case, but also the monetary parts ... and I suspect the Chinese authorities will use that," said Jim McCafferty, head of equity research, Asia ex-Japan, at Nomura.
China's central bank said late on Wednesday it was adjusting policy to benefit more small firms that are having trouble obtaining financing, in its latest move to ease strains on the private sector, a key job creator.
While more fiscal and monetary policy support had been expected in coming months on top of modest measures last year, some analysts wonder if more forceful stimulus will be needed to stabilise the world's second-largest economy.
Currency markets saw a wild spike in volatility in early Asian trade, with the yen moving sharply higher against the U.S. dollar, breaking key technical levels and triggering stop-loss sales of U.S. and Australian dollars.
The dollar was last 1 percent weaker against the yen at 107.77, having earlier fallen as low as 104.96, its lowest level since March 2018. The Australian dollar at one point hit levels against the Japanese yen not seen since 2011.
The euro was up 0.3 percent, buying $1.1375, and the dollar index, which tracks the U.S. currency against a basket of major rivals, was 0.3 percent weaker at 96.52.
Germany's 10-year bond yield was most recently at 0.185 percent, after hitting a session low of 0.148 percent .
U.S. crude oil fell 0.9 percent to $46.12 a barrel, and Brent crude was down 0.2 percent at $54.82. Slowing global growth is expected to coincide with an increase in crude supply, depressing prices.
Gold was higher as the dollar weakened, with spot gold trading up 0.2 percent at $1,289.4 per ounce.
Reporting by Andrew Galbraith, Josephine Mason and Helen Reid; Editing by Kim Coghill/Keith Weir/ Kirsten Donovan