Live updates: Follow the latest news on Israel-Gaza
Yemen's Houthis vowed to prevent Israel-linked ships from passing through the Indian Ocean towards the Cape of Good Hope, the group's leader Abdul Malik Al Houthi has said.
"Our main battle is to prevent ships linked to the Israeli enemy from passing through not only the Arabian Sea, the Red Sea and the Gulf of Aden, but also the Indian Ocean towards the Cape of Good Hope," Mr Al Houthi said in a televised speech.
"This is a major step and we have begun to implement our operations related to it."
Since November, the Iran-aligned group has been attacking ships in the Red Sea and Gulf of Aden in what it says is a campaign of solidarity with Palestinians during Israel's war in Gaza.
Mr Al Houthi said about 34 Houthi members have been killed since the group began the attacks, which have been aimed at 73 ships.
Months of Houthi attacks in the Red Sea have disrupted global shipping, forcing companies to re-route to longer and more expensive journeys around southern Africa.
They have stoked fears that the Israel-Gaza war could spread to destabilise the wider Middle East.
Houthi rebels disrupt ships in the Red Sea - in pictures
The turmoil from Israel's war with Hamas has spilled over to some extent into other parts of the Middle East.
Apart from the Houthi attacks on vital shipping lanes, Lebanon's Iran-backed Hezbollah group is trading fire with Israel along the Israel-Lebanon border, and pro-Iran Iraqi militias have attacked bases that host US forces.
The US and Britain have launched strikes on Houthi targets in Yemen. The US has redesignated the militia as a terrorist group.
A US State Department representative said it was aware of the reports.
"Houthi threats only put further distance between Yemen and the peace process, which the Yemeni people keenly deserve," the representative said.
They referred to President Joe Biden's State of the Union address, in which he said: “Creating stability in the Middle East also means containing the threat posed by Iran.
"That’s why I built a coalition of more than a dozen countries to defend international shipping and freedom of navigation in the Red Sea.
"I ordered strikes to degrade the Houthi capability and defend US forces in the region.”
A representative for US Central Command said on Wednesday that the Houthis have "targeted all internal shipping, not only those linked to Israel".
"The Houthis remain an ongoing concern for all nations that engaged in maritime commerce in the region," the Centcom representative said.
The group has access to and is provided with weapons and support by Iran, and Washington has not seen that support "lag in any way".
The representative said the US will continue to support regional stabilisation efforts through Operation Prosperity Guardian.
