The leader of Yemen's Houthis, Abdul Malik al-Houthi, said on Thursday the group would target ships of any company related to supplying or transporting goods to Israel regardless of their destination.
He said this was a fourth stage of escalation in retaliation to "the Israeli aggression on Rafah" in the southern Gaza Strip.
"From now on, we are also thinking about the fifth stage and the sixth stage, and we have very important, sensitive and influential choices on the enemies," he added.
Months of Houthi attacks in the Red Sea have disrupted global shipping, forcing firms to re-route to longer and more expensive journeys around southern Africa, and stoked fears that the Israel-Hamas war could spread to destabilise the wider Middle East.
The United States and Britain have carried out strikes against Houthi targets in response to the attacks on shipping.
By Clauda Tanios and Ahmed Tolba