French prosecutors have opened a serious fraud investigation into Volkswagen over devices the German automaker fitted into cars to cheat emissions tests, a judicial source told AFP on Tuesday.

Oil prices retreated Tuesday, with Brent crude back below $40 a barrel, after Kuwait reportedly ruled out cutting output, analysts said.

Prices had strengthened earlier in the day, extending recent strong gains won largely on hopes of oil production freezes to ease a global supply glut. 

The South African government said Tuesday that exploration for shale gas will begin in the next 12 months, ending years of speculation over the project.

South Africa's semi-desert Karoo region is believed to hold at least 485 trillion cubic feet of shale gas, but drilling has been delayed by environmental and economic concerns.

World stock markets sank deep into the red on Tuesday, as China released data showing another hefty slump in exports, sparking renewed worries over the nation's powerhouse economy.

China's exports dived more than a quarter on-year in February, new data showed Tuesday, while imports were almost 14 percent off -- far worse than forecast.

Oil prices dipped in Asia Tuesday but Brent crude stayed above $40 a barrel, as traders took profits after solid gains over the past three weeks.

Prices have strengthened following talks of a production freeze, with a producers meeting mooted on March 20 in a bid to ease a global supply glut that has depressed the market.

German industrial production jumped unexpectedly in January, propelled by increased activity in the manufacturing and construction sectors, the economy ministry said on Tuesday. 

The ministry calculated that factory output -- a key yardstick for gauging the health of Europe's biggest economy -- leapt by 3.3 percent in January compared with a month earlier, corrected for seasonal factors.

The United States said Monday it is placing trade restrictions on Chinese telecommunications equipment giant ZTE due to violations of U.S. sanctions on Iran.

Bangladesh's central bank said Monday that part of almost $100 million allegedly stolen from a reserve account in the United States last month has been recovered.   

Eurozone finance ministers met Monday to defuse a bitter rift between top EU and IMF officials over how strictly to hold Greece to the ambitious reform commitments made as part of its bailout.

Emirati Oil Minister Suhail Mazrouei said Monday that current market prices are forcing most producers to freeze oil output levels, insisting it made "no sense" to pump more crude.

"Current prices are forcing everyone to freeze. So I think it is happening as we speak," Mazrouei told reporters in Abu Dhabi.