LONDON — Oil prices saw their biggest daily gain since the 1991 Gulf War on Monday after drone attacks on two Saudi oil facilities, fuelling fresh geopolitical and growth fears.

Europe's benchmark Brent crude surged by 20 percent and US counterpart WTI by 15 percent as commodities trading got underway after President Donald Trump warned that the US was "locked and loaded" to respond to the attacks that Washington blamed on Iran.

Brent North Sea crude jumped 12.2 percent at $67.55 per barrel, while West Texas Intermediate surged 11.7 percent at $61.24.

Both contracts later came off their peaks, but were still up around 12 percent at the close of European trading.

The price surges weighed across world stock markets on fears that a sustained higher cost of crude could impact already weakening global economic growth.

"Growing tensions in the Middle East are another headwind for the global economy in already uncertain times and a full-blown conflict could trigger another leg in the global downturn," said Jennifer McKeown, head of Global Economics at Capital Economics.

However, share prices of energy majors jumped, with traders seeing higher profits down the line for the likes of BP and Shell.

In foreign exchange, the dollar was down against the yen and up against the euro, while the pound slid, with the EU saying that Britain had offered no new, viable Brexit proposals after Prime Minister Boris Johnson held Brexit deal talks with EU chief Jean-Claude Juncker.

Gold, which along with the yen is seen as a haven in times of geopolitical and economic unrest, rose.

Markets' focus was firmly on oil however after the weekend attack that was claimed by Tehran-backed Huthi rebels in neighboring Yemen.

"Oil price shocks like this are bad news for growth," Neil Wilson, chief market analyst at trading group Markets.com, told AFP.

"It raises stagflation risks too – higher oil prices suppress growth and raise inflation. Of course it depends how long this lasts, does the risk-premium mean higher prices for the rest of the year or does it fade quickly if it comes back on stream this week?"

Saudi Energy Minister Prince Abdulaziz Bin Salman on Sunday said the kingdom would use its vast inventories to partially compensate for the lost production and the US also authorized the release of its reserves.