Friday's spike in crude oil prices—which increased by more than 4%—was caused by the Middle East crisis, which saw Israel bomb Iran. The world benchmark for crude oil, Brent, suddenly surged past $90 per barrel.

West Texas Intermediate (WTI) crude futures in the US increased by 4.06% to $86.09, while Brent oil increased by 3.94% to $90.54 a barrel. The news that Israeli rockets had struck a location in Iran caused oil prices to soar. Isafahan, an Iranian city, had explosions at an airport, according to the Fars news agency.

Crude oil prices have been climbing all year long due to tightening market conditions spurred on both OPEC output curbs and mounting tensions in the Middle East.

Investors have been keeping a close eye on Israel's response to the Iranian drone assaults on April 13. Earlier in the week, there was a notion that international pressure would mitigate any Israeli retribution to Iran's strike, hence reducing the geopolitical risk premium in oil prices.

Venezuela suffered a blow to the world's crude oil supply when it lost a key US license that allowed the OPEC member to ship oil anywhere in the globe. Following Iran's drone strike on Israel this weekend, the US placed sanctions on the country, another member of OPEC, targeting its unmanned aerial vehicle program.

But Iran's oil sector is not included in these sanctions.

According to the state-run IRNA news agency, Iran allegedly activated its air defense systems early on Friday morning in response to reports of explosions close to a significant airfield in Isfahan.

It was unclear at the moment if Iran was being attacked. But when Iran launched an unprecedented missile and drone attack on Israel, tensions persisted. The Israeli military declined to comment on the situation right away.

Iran launched these missiles following an attack on sites in and around Israel the Saturday before, according to Israeli military sources. Iran launched more than 300 unmanned drones and missiles as part of the strike.