Yemen ‘s Iranian-backed Houthi rebels captured the island of Mayun at the entrance of the Red Sea, a key alternative for shipping Saudi oil and other exports since Iran has been targeting vessels in the Strait of Hormuz.

The island’s seizure was confirmed by a senior military official with Yemen’s internationally recognized government and a Houthi official. Both spoke on condition of anonymity because they were not authorized to talk to journalists.

About 12% of the world’s goods are typically shipped through the Bab el-Mandeb Strait at the southern end of the Red Sea. It’s especially important to Saudi Arabia, a key U.S. ally.

The Houthis’ military spokesperson, Yahya Saree, said in a statement Friday that “maritime navigation is safe for all companies except for Saudi vessels.” But markets are nervous, and experts have described the Houthis as highly unpredictable.

A United Nations spokesperson, Farhan Haq, said Houthi rebels in Mokha seized a compound that had housed U.N. staff, who all fled safely before the city’s capture. Haq said that “no U.N. personnel remain in Mokha right now.”

Saudi Arabia shuts down oil pipeline, citing attacks

Saudi Arabia said Friday it had shut down a major, cross-country oil pipeline as a “precautionary measure” following attacks the day before. The Saudi Energy Ministry did not say who carried out the attacks.

The East-West pipeline has been vital to Saudi Arabia continuing oil exports in the months since the Iran war has disrupted shipping in the Strait of Hormuz.

In a statement early Saturday, the Iraqi government said Prime Minister Ali al-Zaidi ordered an investigation into the operations command in Maysan province and dismissed its commander after authorities determined that attacks targeting Saudi Arabia were launched from a site in the province.

According to the International Energy Agency, Saudi oil exports through the Red Sea port at the pipeline’s end have more than doubled since the U.S. and Israel attacked Iran on Feb. 28.