Oil prices hit a two-month high on Monday, lifted by a tightening US crude market and the threat of sanctions against Opec-member Venezuela.

Brent crude futures, the international benchmark for oil prices, were at $52.67 per barrel early on Monday, up 15 cents or 0.3%. Prices hit $52.76 per barrel earlier in the day, their highest since 25 May.

US West Texas Intermediate crude futures were up 16 cents, or 0.3%, at $49.87 per barrel, the highest since 30 June.

The price rises put both crude benchmarks on track for sixth consecutive session of gains.

Oil prices have risen around 10% since the last meeting of leading members of Opec and other major producers, including Russia, when the group discussed potential measures to further tighten oil markets.

"A combination of factors seems to be driving the newly found optimism. US inventories are showing massive drawdowns, Saudi Arabia seems intent on playing its role as the world's swing producer (and) impending sanctions on Venezuela by the US will almost certainly be oil price supportive," said Jeffrey Halley, senior market analyst at futures brokerage OANDA in Singapore.

The United States is considering imposing sanctions on Venezuela's vital oil sector in response to Sunday's election of a constitutional super-body that Washington has denounced as a "sham" vote.

But traders said the biggest price supporter was currently a tightening US oil market.

"Strong increases in the price of oil ... (were) fuelled in large part by the substantial draw-downs in US inventories over the past several weeks," said William O'Loughlin, investment analyst at Australia's Rivkin Securities.

"A continuation of this trend could indicate the oil market is rebalancing thanks to the production cuts by Opec and Russia," he added.

After rising by more than 10% since mid-2016, US oil production dipped by 0.2% to 9.41 million barrels per day in the week to 21 July.

US crude inventories have fallen by 10% from their March peaks to 483.4 million barrels.

Drilling for new US production is also slowing, with just 10 rigs added in July, the fewest since May 2016.

The tighter market was also visible in the price curve, which shows backwardation in the front end.

Backwardation is a market condition in which prices for immediate delivery of a product are higher than those later on.

Brent prices for delivery in September are currently around 35 cents above those for October.