The price of oil and gold spiked and stocks sold-off on Friday, after a US airstrike on a top Iranian general fuelled fears of conflict in the region.

The US Department of Defense said in a statement released early on Friday morning that it had killed the head of the Islamic Revolutionary Guard’s elite Quds Forces in an airstrike.

The US said the strike on Qassem Soleimani was ordered directly by US President Donald Trump.

The Department of Defense said Soleimani was behind the recent attacks on the US embassy in Baghdad and said the “strike was aimed at deterring future Iranian attack plans.” It labelled Soleimani’s unit terrorists.

“The United States will continue to take all necessary action to protect our people and our interests wherever they are around the world,” the US government said.

Iranian leader Ayatollah Ali Khamenei said there would be “revenge” for the strike, according to Iranian news service Fars, and declared a period of mourning for Soleimani’s death.

The US Embassy in Iraq on Friday told American citizens to leave the country “due to heightened tensions in Iraq and the region.”

Oil prices spiked in response to the news, as traders weighed the possibility of disruption to supply from the region. Iran sits on the Strait of Hormuz, a crucial water pathway in the global oil trade. Capital Economics said that Brent oil could climb as high as $150 per barrel if Iran tried to blockade the passage.

Crude oil (CL=Z) was up 3.4% to $63.30 per barrel by afternoon in London. Brent (BZ=F) was up 3.5% to $68.61 per barrel at the same time.

READ MORE: What a US-Iran war could mean for the economy

Gold (GC=F) also jumped. The ‘safe haven’ asset rose 1.4% to $1,550.90 per ounce, the highest price since September.

Stocks sold off on the air strike news. Equities tend to rise when investor risk appetite is high and fall when people are wary. The FTSE 100 (^FTSE) was down 0.4% in early trade, but recovered to trade up 0.1% by the afternoon.

Germany’s DAX (^GDAXI) fell by 1.3% and the CAC 40 (^FCHI) in France was flat. In the US, the S&P 500 (^GSPC) fell 0.6%, the Dow (^DJI) fell 0.8%, and Nasdaq (^IXIC) lost 0.7%.

Research consultancy Eurasia Group said Friday the chance of a conflict between the US and Iran had now risen to 40%. Rachel Washburn, a geopolitical strategy associate at Academy Securities, called the strike “the most destabilizing event in the region since we invaded Iraq.”

Connor Campbell, a financial analyst at trading platform SpreadEx, said: “Though Suleimani may be unknown by many in the West, some political analysts have likened him to a US vice president in terms of profile, while he has previously been described as the ‘single most powerful operative in the Middle East.”