Oil prices rose on Friday and were on track for a fourth monthly gain ​as traders braced for a potential escalation in the US-Iran conflict after the US midterm elections, with an attack on a tanker in the ‌Strait of Hormuz highlighting supply risks from the war.

Brent crude futures for December , which expire on Friday, were up $2.26, or 2%, at $117.14 a barrel as of 1236 GMT. The more active January contract gained $2.30 to $113.10.

US West Texas Intermediate (WTI) crude futures climbed $1.94, or 1.9%, to $103.94.
For the month, Brent was on course to finish 13% higher, while WTI was heading for ​a 15% jump.

“The oil market is getting increasingly spooked as we approach the midterms,” said Ole Hansen, head of commodity strategy at Saxo ​Bank. Some investors and analysts are expecting another resumption of US attacks on Iran after the elections, he said.

On Friday, a ⁠tanker in the Strait of Hormuz — the key sea outlet for Gulf crude and fuel supplies — was hit by explosive devices attached by a small boat, ​the UKMTO said. It was not immediately clear who was behind the attack.

It was the first known successful strike using limpet mines, explosives which are attached ​to a ship’s hull by a small boat, in the waterway since the US war with Iran began in February, maritime sources said.

“Continued kinetic action around the Strait of Hormuz amidst doubts of a viable diplomatic pathway are keeping oil prices elevated in expectation of an escalation of the conflict in coming weeks,” said Saul Kavonic, head of energy research ​at MST Marquee.