Yemen's Tehran-backed Houthis captured more islands in the southern Red Sea, government and Houthi officials said Monday, strengthening their control of a major maritime shipping route.

The capture of the islands of Greater and Lesser Hanish is the latest in the group's swift advance around the Bab el-Mandeb Strait, a key passage for oil shipments that has become even more crucial during the Iran war as the Strait of Hormuz remains under US and Iranian blockades.

Like Hormuz, located at the mouth of the Persian Gulf, the Bab el-Mandeb Strait — on the opposite side of the Arabian Peninsula — is a chokepoint that connects the Indian Ocean to the Red Sea, making it a key waterway for cargo traffic to the Mediterranean Sea.

For more than a month, the Houthis have been striking Saudi oil infrastructure and shipping in the Red Sea, stepping up pressure on global oil prices and boosting Iran's leverage in its war with the US.

Forces of the internationally recognised Yemeni government have been attempting to rally and fight back, but the Houthi gains have seemingly come with little resistance.