Two more major shipping firms, Mediterranean Shipping Company and CMA CGM, said on Saturday they were suspending passage through a Red Sea strait vital for global trade after Yemeni rebel attacks in the area.
The announcement by Italian-Swiss giant MSC and France's CMA CGM follows a similar decision on Friday by two of the world's largest shipping companies, Maersk and Hapag-Lloyd, in response to a warning by the Iran-backed Huthi rebels.
The Huthis, who control much of Yemen but are not recognised internationally, said they were targeting vessels to pressure Israel over its devastating war with Palestinian Hamas militants in the Gaza Strip.
Earlier on Saturday, the UK government said one of the country's destroyers had brought down a suspected attack drone in the Red Sea, adding to concerns that the Gaza conflict could spread.