Crude oil futures rose on Monday, although concerns about the long-term outlook for demand dragged on prices.

Crude markets were also supported in the wake of data that showed South Korea did not import any oil from Iran in September for the first time in six years, before US sanctions against the Middle Eastern country take effect in November.

Brent crude had risen $1.01, or 1.26 percent, to $81.44 a barrel on Monday, on track for its biggest daily gain since October 9.

"The market has again expressed concerns over geopolitical tensions in the Middle East after US and Saudi traded comments over the disappearance of the Saudi journalist, leading to a jump in prices," Wang Xiao, head of crude research with Guotai Junan Futures, wrote in a research note.

Jamal Khashoggi, a US resident who wrote columns for the Washington Post critical of Saudi Crown Prince Mohammed bin Salman, disappeared on October 2 during a visit to the Saudi consulate in Istanbul, Turky. Since then, Saudi Arabia has been under pressure.

Lingering geopolitical worries, trade concerns and a weaker economic outlook may pave the way for another week of volatile trading, Chen said, adding that Monday's recovery in prices was "fragile".

Putting downward pressure on oil prices, the International Energy Agency, the West's energy watchdog, said in its monthly report that the market looked "adequately supplied for now" and trimmed its forecasts for world oil demand growth this year and next.

That comes after the secretary general of the Organization of the Petroleum Exporting Countries (OPEC) last week said the group sees the oil market as well supplied and that it was wary of creating a glut next year.