Oil prices briefly spiked above $100 per barrel early Thursday as seven tankers were attacked by Iran in a two-day period across the Persian Gulf and the Strait of Hormuz.

The two most damaging attacks, apparently carried out by explosive-laden boats, hit the tankers Safesea Vishnu and Zefyros in Iraqi waters, killing at least one crew member and setting the vessels ablaze.

Iran’s Islamic Revolutionary Guard Corps (IRGC) claimed responsibility for the attacks, releasing a video of the burning Safesea Vishnu in which a man can be heard shouting: “Allah is the greatest! The destruction of an American tanker in the northern district of the Persian Gulf! I obey you Khamenei! Hail be the Islamic Republic of Iran! Soldiers of the Islamic Revolutionary Guard Corps Navy!”

The attacks followed projectile strikes on four ships in the Strait of Hormuz since Wednesday and caused Brent crude futures to jump past the century mark before falling back to around $96.50 per barrel as of 7 a.m. ET.

Hours later, a seventh vessel, the container ship Source Blessing, was “hit by some kind of fragments” near the Jebel Ali port in the United Arab Emirates, causing a small fire, but no injuries.

“It’s now very difficult to sail in the Persian Gulf,” Nils Haupt, a spokesman for Germany-based ship owner Hapag-Lloyd, told the Wall Street Journal.

Thursday’s attacks followed President Trump ordering the release of 172 million barrels of oil from the US Strategic Petroleum Reserve in an effort to bring down gas prices that have surged by an average of 60 cents per gallon nationwide since America and Israel began joint attacks on Iran Feb. 28.

The IRGC has warned that any vessel which attempts to traverse the Strait of Hormuz, which connects the Persian Gulf with the Gulf of Oman and the Arabia Sea and through which an estimated one-fifth of the world’s oil passes, is subject to attack.

“Expect oil at $200 per barrel,” a spokesperson said in a statement Wednesday aimed at the US. “The price of oil depends on regional security, and you are the main source of insecurity in the region.”

White House press secretary Karoline Leavitt told reporters Tuesday that President Trump “has offered the US Navy to escort tankers when necessary.”

However, Energy Secretary Chris Wright confirmed to CNBC Thursday morning that such escorts were not yet possible.

“It’ll happen relatively soon but it can’t happen now,” Wright said. “We’re simply not ready. All of our military assets right now are focused on destroying Iran’s offensive capabilities and the manufacturing industry that supplies their offensive capabilities.”

Earlier Thursday, the United Kingdom Maritime Trade Operations Centre said an unidentified projectile struck a container ship 35 nautical ‌miles north ‌of Jebel Ali in the United Arab Emirates, causing a small fire. The crew were reportedly safe.

The Thai-flagged Mayuree Naree dry bulk vessel was struck by “two projectiles of unknown origin” while sailing through the strait on Wednesday, causing a fire and damaging the engine room, the ship’s Thai-listed operator Precious Shipping said in a statement.

“Three crew members are ⁠reported missing and believed to be trapped in the engine room,” Precious Shipping said.

“The company is working with the relevant authorities to rescue these three ⁠missing crew members,” it said, adding that the remaining 20 crew members had been safely evacuated and were ashore in Oman.

Images shared by the Thai news outlet Khaosod English showed what were reported to be crew members of the ship after their rescue by Oman’s navy.

The Japan-flagged container ship ONE Majesty also sustained minor damage on Wednesday from an unknown projectile 25 nautical miles northwest ⁠of Ras Al-Khaimah in the UAE, two maritime security firms said.

Japanese owner Mitsui OSK Lines and a spokesperson for Ocean Network Express, its charterer, said the vessel was struck while at anchor in the Gulf and an inspection of the hull revealed minor damage above the waterline.

All crew members are safe, they said, adding that the vessel remains fully operational and seaworthy. The owner said the cause of the incident remained unclear and was under investigation.

A fourth vessel, a bulk ‌carrier, was also hit by an unknown projectile about 50 nautical miles northwest of Dubai, maritime security firms said.

The projectile had damaged the hull of the Marshall Islands-flagged Star Gwyneth, the maritime risk management company Vanguard said, adding that the vessel’s crew was safe. Owner Star Bulk Carriers said the ship was hit in the hold area while it was anchored. There were no crew injuries and no listing.

With Post wires