Yemen’s Iran-aligned Houthis edged closer on Thursday to gaining leverage over the Bab el-Mandeb Strait, one of the world’s most important routes for commodity vessels, four Yemeni government military sources said, as fighting with Saudi-backed forces tilts towards a resumption of full-scale war.

The Houthis were nearing complete control of coastal cities such as the historic port of Mocha and Dhubab that sit directly along the strait, as they push to take over the whole Yemeni Red Sea coast, the sources said.

In recent days there has been an escalation in fighting between Saudi Arabia’s Yemen allies in the internationally backed government and the Houthis, a second theatre of war in the Iran conflictthat threatens global energy supplies. A U.N.-brokered truce in 2022 largely halted years of war but remains fragile.

Houthis push towards Bab el-Mandeb

Bab el-Mandeb, or the Gate of Tears, named for its perilous navigation conditions, is the southern outlet of the Red Sea, between Yemen on the Arabian Peninsula and Djibouti and Eritrea on the African coast, making it a major prize for the Houthis, who control Yemen’s most populous areas and much of the north.

Why the strait matters for global shipping

It is one of the world’s most important routes for crude oil and fuel from the Gulf bound for the Mediterranean via the Suez Canal or the SUMED pipeline on Egypt’s Red Sea coast, as well as commodities bound for Asia, including Russian oil.

Blocking the narrow passage would isolate Gulf oil-producing countries such as energy superpower Saudi Arabia from their main shipping routes after Iran effectively closed the Strait of Hormuz — the primary maritime energy artery between Asia and Europe.

Saudi Arabia and Houthis exchange attacks

The Houthis said on Wednesday that Saudi strikes hit the Yemeni provinces of Jawaf, Marib and Saada, bordering the kingdom, as well as the provinces of Taiz in the south and al-Hodeidah along the Red Sea coast, a Houthi stronghold used as a base for their broader campaign of attacks on shipping in the waterway. Saudi Arabia did not confirm the strikes.

Saudi civil defence authorities issued an all-clear on Thursday following an emergency alert declared in the southwestern province of Khamis Mushait for the fourth time in 24 hours, as clashes flared with the Houthis.

The danger had passed, the civil defence officials said shortly after the alert.

At least 73 people were wounded in four southern Saudi cities, including Khamis Mushait, in recent Houthi attacks on the world’s largest oil exporter, the Saudi-led coalition said on Tuesday.

The militant group said it attacked an airbase in Khamis Mushait and oil infrastructure in nearby cities in one of the biggest attacks on Saudi Arabia since the start of the U.S.-Israeli war on Iran in February.

The coalition said the Houthis continued their attacks on national assets and infrastructure on Wednesday.