Global shares eased for a third day on Friday, on course for their longest losing streak in over a month, and yields on some lower-rated euro zone bonds rose as a gloomier economic picture in Europe led investors to shed riskier positions.

Weaker-than-forecast GDP figures from euro zone countries such as Italy, France and Portugal on Thursday challenged market expectations for an economic recovery in the bloc, which have boosted shares and lower-rated bonds in the region since last summer.

Sharp sell-offs in U.S. and Japanese shares and a fall in safe haven Treasury yields strengthened the feeling global investors were starting to question a 20 percent rally in global shares since June 2013, which propelled a key world index to 6-1/2 year highs earlier this week.

"There's a general rotation and fall in risk appetite," Andrew Parry, chief executive officer at Hermes Sourcecap, which manages 2.4 billion euros ($3.3 billion) worth of assets.

"In Europe...GDP figures yesterday show the recovery is quite modest so far."

The MSCI All-Country World index was down 0.2 percent, falling for a third day and further retreating from 418.24, a high touched on Thursday and previously not seen since Nov. 2007.

Futures pointed to a flat to lower start for U.S. indexes, which have fallen for the past two sessions.

Greek and Portuguese 10-year government bond yields rose, hit by nervousness around Greek government stability and weaker-than-expected growth data for Portugal.

"There will be some investors that are concerned and should take into consideration that is not just a one day movement but something more prolonged," said Daniel Lenz, strategist at DZ Bank.

Italian, Spanish and Irish bond yields reversed early advances to trade slightly lower.

Yields on benchmark German bonds, regarded as a safe-haven asset due to the country's strong economy, hovered close to a one-year low while the euro consolidated just above a 2-1/2-months trough against the dollar.

In commodities, gold struggled below $1,300 an ounce after U.S. jobs and factory data indicated brighter prospects for that economy, hurting the metal's appeal as an investment hedge.

Nickel prices rose on Friday, shaking off steep losses from the previous two sessions as investors refocused on shrinking supplies, while copper prices were on track to post their biggest weekly gains in nearly two months on robust demand.

Brent futures held above $109 a barrel as fresh tensions over Ukraine kept them on course for their biggest weekly rise since mid-April, but returning Libyan supply capped gains.