Saudi Arabia and the disappearance of Jamal Khashoggi in brief

Crude oil futures rose sharply on Monday as geopolitical tensions over the disappearance of a reputed Saudi journalist fueled supply concerns, although worries about the long-term prospects of demand weighed on prices.

Crude markets were also buoyed by data showing that South Korea was not importing Iranian oil in September for the first time in six years, before US sanctions against the Middle East country took effect in November.

Brent rose 98 cents, or 1.22 percent, to $ 81.41 a barrel, at 12 hours 124 GMT, on its way to its biggest daily gain since Oct. 9.

US crude futures rose 80 cents, or 1.12 percent, to $ 72.15 a barrel, extending gains they made on Friday after heavy losses Wednesday and Thursday.

"The market has again raised concerns over geopolitical tensions in the Middle East after the US and Saudi Arabia have exchanged comments on the Saudi journalist's disappearance, resulting in higher prices," wrote Wang Xiao, head of crude research at Guotai Junan Futures a research note.

Saudi Arabia has been under pressure since Jamal Khashoggi, a prominent Riyadh critic and US resident, disappeared on October 2 after visiting Saudi Arabia's consulate in Istanbul.

The kingdom will retaliate against possible economic sanctions taken by other states, the official SPA news agency reported on Sunday, citing an official source.

Meanwhile, South Korea has stopped importing Iranian oil for the first time in years.

"South Korea's decision to prevent Iranian oil imports from giving the market confidence in pricing," said Chen Kai, head of research at Shengda Futures, a futures broker.

Persistent geopolitical concerns, trade concerns and weaker economic prospects could pave the way for another week of unstable negotiations, Chen said, adding that Monday's price recovery was "fragile".

The International Energy Agency, the West's energy watchdog, pointed out in its monthly report that the market seemed "adequately supplied" and has reduced its growth forecasts for global oil demand this year and next year.

This comes after the Secretary General of the Organization of the Petroleum Exporting Countries (OPEC) said last week that the group believes the oil market is also well supplied and that it feared creating an overabundance next year.