(Bloomberg) -- Oil surged after fresh fighting flared up in the Strait of Hormuz, highlighting risks to flows from the Middle East after months of conflict.

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Brent for November rose above $90 a barrel, while West Texas Intermediate was near $86. The US military struck Iranian rocket launchers preparing to send mines into the waterway on Sunday, according to Captain Tim Hawkins, a spokesperson for US Central Command, ending weeks of relative calm.

Crude is wrapping up a volatile month in which Brent futures have swung in a range of almost $17 a barrel. Prices have been buffeted by stop-start efforts to bring an end to the fighting, as well as a pledge by Washington that it will try to force Tehran to capitulate by ramping up efforts to isolate and cripple Iran's economy. Still, analysts have been underwhelmed by the US actions.

Still, even without a peace deal between Washington and Tehran, about 6 million to 8 million barrels a day of crude are moving through Hormuz, according to traders monitoring cargoes. Separately, Iran's semi-official Mehr news agency reported that vessel traffic along a route approved by the Islamic Republic "is taking place on a limited basis," with ships sakid to be paying tolls.

Trading in Brent futures may be lower than usual in Monday's session, with parts of the UK including England marking a national holiday.