Global shares fell to a six-month trough and Brent crude futures tumbled to their lowest since 2010 on Friday as investors worried about the prospect of a widespread economic slowdown just as U.S. monetary stimulus nears its end.

Assets which depend on economic growth, such as shares and oil, have been hit by a raft of weak indicators from Europe at a time when other big economies, including China, Japan and Brazil face their own hardships.

Meanwhile, the U.S. Federal Reserve is set to wind down later this month the asset purchase program that has boosted marketsover the past two years. Many observers doubt the recent stimulus measures unveiled by the European Central Bank will make up for it.

"There has been a barrage of negative thoughts on growth and growth assets," said Stewart Richardson, a partner at macro hedge fund RMG Wealth Management.

"I believe we're entering a bear market. We've been trying to be short equities and we've been focusing our shorts in Europe and small caps," he said, referring to bets that shares in those markets will keep falling.

The MSCI All-Country World index .MIWD00000PUS fell 0.8 percent to its lowest level since April 18 at 403.54 points, taking its loss since the start of the week to 1.9 percent.

The index, which is eyeing its third consecutive weekly fall, has retreated by roughly 7 percent since testing an all-time high last month.

Germany's DAX index .GDAXI sank to a near one-year low while U.S. index futures SPc1 NDc1 NDc1 suggested shares on Wall Street were set to add to Thursday's sharp losses. [.EU] [.N]

A string of dismal data from Germany and other large euro zone economies in recent weeks has fed anxieties about a possible recession in the region while the jury is still out on the European Central Bank's proposed policy response.

The ECB's secured debt buying programs, a key part of the bank's latest package, has yet to kick in and some investors are doubtful it will be sufficient to shore up growth and inflation in the currency bloc while the Fed reins in its own stimulus.

Some investors have been speculating that the ECB will be forced to launch a sovereign bond-buying program, styled on the Fed's quantitative easing (QE).

"I've been taking profits but I would not necessarily run and hide from European equities," said Caroline Vincent, European equities fund manager at Cavendish Asset Management.

"The poorer the data gets, the more likely it is that the ECB will do QE."

Meanwhile, concerns on global growth hit oil prices hard. European benchmark Brent crude oil LCOc1 fell 0.7 percent to $89.42, having hit its lowest level since December 2010 at $88.11.

"It's panic mode. Panic and capitulation," said Carsten Fritsch, commodities analyst at Commerzbank. "We are now in uncharted territory, so anything could happen."

Euro zone bond yields bounced off record lows after top Federal Reserve officials hinted at an interest rate rise in the middle of next year, reversing some of the bets for a longer period of near-zero rates. [GVD/EUR]

The dollar also inched higher but was still on course to end a record-long rally with its first weekly fall in three months. [FRX/]