Yemen's Iran-backed Houthi rebels said on Saturday they have forced eight Saudi oil tankers to change course, as part of a blockade of Saudi energy exports.
The tankers will now have to reroute via the Cape of Good Hope in South Africa to reach their destination, the Houthis said, a move would significantly lengthen voyages to Asia.
Saudi Arabia has so far not confirmed the claims.
Last week, the Houthis announced they had imposed a naval blockade on Saudi Arabia in response to what the rebel group describes as a long-standing Saudi siege on the Houthi-ruled areas in Yemen.
Yemen has been locked in a devastating conflict since the Houthi rebels took over the capital Sana'a and other parts in northern Yemen in late 2014.
Since then, Saudi Arabia been leading a coalition to support the Yemeni government against Houthi advances.
Tensions between the Houthis and Saudi Arabia escalated again amid the US-led war on Iran. The Iran-backed group controls the Bab al-Mandab Strait, a key transit point for global shipping that connects the Red Sea with Asia.
Fears are running high that the Houthis' threats could effectively lead to the closure of the choke point, exacerbating the situation for global trade already struggling due to the closure of the Strait of Hormuz.
However, ships appear to continue to travel through the Bab al-Mandab, with data provider Kpler reporting on Friday that 47 had crossed the strait in both directions.
The Houthis also said they had no plans to impose transit fees on ships passing through the waterway.