Hong Kong/London CNN Business  — 

Oil prices moved higher Friday after a top Iranian general was killed in a US airstrike ordered by President Donald Trump.

Futures for Brent crude, a global benchmark, jumped 3.6% to settle at $68.60 per barrel on Friday. US oil futures gained 3.1%, settling at $63.05 per barrel. Both are on track for their biggest daily gains in about a month and their highest prices since September, when Iran attacked Saudi oil facilities.

Qasem Soleimani, commander of the Quds Force of Iran’s Islamic Revolutionary Guards Corps, was killed in the strike at Baghdad International Airport.

The Pentagon said that Soleimani was “actively developing plans to attack American diplomats and service members” and that the strike was aimed at “deterring future Iranian attack plans.”

The killing of the powerful Iranian general risks further escalating tensions in the Middle East, which is home to major oil producing countries and key energy supply routes.

Iranian President Hassan Rouhani said in a statement that his country would take revenge for the killing of Soleimani.

“An indirect response is the most apparent course of action, and oil installations and tankers were my first thoughts,” said Jeffrey Halley, senior market analyst for Asia Pacific at Oanda, in a research note.

But Halley added that it’s hard to tell whether Friday’s surge will be sustained.

Oil prices spiked more than 14% in September after coordinated attacks on crucial Saudi Arabian energy production facilities disrupted 5% of the daily global oil supply.

The United States blamed Iran for those attacks, but prices pulled back quickly after Saudi officials said the kingdom would rely on reserves to keep exports stable. Iran denied that it was responsible. It took Saudi Arabia just 11 days to restore production, according to the International Energy Agency.

A spate of attacks last year on oil tankers near the Iranian coast also demonstrates the potential for market disruption.

Two oil tankers were attacked in June near the Strait of Hormuz, a strategic choke point through which roughly 30% of the world’s sea-borne crude oil passes.

“Given the scope for tension to persist in the Strait of Hormuz, a protracted period of higher oil prices has to be a risk,” said Kit Juckes, a strategist at Societe Generale.

Stock markets sag

There were other signs of investor unease on Friday.

The price of gold, which traders tend to buy in times of uncertainty, increased by 1.3% to $1,547.89 per ounce. The Japanese yen, another safe haven, strengthened 0.4% against the US dollar.

Elsewhere on Friday, major Asian stock indexes reversed earlier gains and traded lower following the news.

Hong Kong’s Hang Seng (HSI) Index shed 0.3%, while South Korea’s Kospi was little changed. China’s Shanghai Composite was down 0.1%, after seesawing between gains and losses.

Japanese markets were still closed for the New Year’s holidays and will resume trading on Monday.

Stocks in Europe were lower in morning trade. The FTSE 100 was down 0.7% in London and Frankfurt’s DAX dropped 1.9%.