Mocha is about 80km from the Bab el-Mandeb Strait, a strategic waterway between the Red Sea and the Gulf of Aden through which about 12 per cent of the world's oil and other goods are shipped.
The Bab el-Mandeb has become even more important for global energy supplies since shipping through the nearby Strait of Hormuz was disrupted by Iran after it was attacked by the United States and Israel in February.
The Houthi rebels' takeover of Mocha was confirmed to the Associated Press by Ahmed Baash, a commander with the National Resistance Forces allied with Yemen's government, and Hazam al-Assad, a member of the Houthis' political bureau.
Yemeni government military sources said the Houthis had gained further leverage over the Bab el-Mandeb Strait, the southern outlet of the Red Sea, and had reached the islands of Hanish.
Mocha represents the Houthis biggest territorial gain since a truce signed in 2022 to end a civil war in Yemen that lasted more than a decade.
Red Sea navigation is safe for all shipping companies except for Saudi vessels, Yemen's Houthi-run humanitarian operations co-ordination centre said in a statement.
Saudi Arabia has relied on the Red Sea shipping route since the Iran conflict effectively closed the Strait of Hormuz, through which a fifth of global oil used to flow.
Houthi spokesman Mohammed Abdulsalam said that operations were defensive and would stop once attacks on Yemen stopped.
Yemeni government forces and their allies are relocating south along the Red Sea coast to Dhubab, which sits directly on the Bab el-Mandeb Strait, across from the island of Perim, government military sources told Reuters.
Control of Dhubab and the island is key to gaining hold of the strait, they said.
Bab el-Mandeb, or the Gate of Tears - named for its perilous navigation conditions - lies between Yemen on the Arabian Peninsula and Djibouti and Eritrea on the African coast, making it a major prize for the Houthi rebels who control Yemen's most populous areas and much of the north.
A return to full-scale civil war would be devastating for the Yemeni people and potentially world energy supplies.
Residents of Mocha have told AP that Houthi forces can be seen all around the city and that markets have shuttered.
Mocha was long held by forces aligned with Yemen's internationally recognised government.
with Reuters
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