A major transport union urged a full halt of merchant ships sailing through the Red Sea, adding to calls for vessels to reconsider the voyages after a Houthi militant attack killed three sailors.

“We call on the industry to divert ships around the Cape of Good Hope until safe transit through the Red Sea can be guaranteed,” the International Transport Workers’ Federation said in a statement. “No delivery window is worth the loss of seafarers’ lives.”

The ITF lobbies for seafarer rights by acting alongside more than 700 affiliate trade unions. It followed a similar appeal by Nautilus International, one of the world’s largest crewing unions earlier Thursday.

Two crew members from the Philippines and another from Vietnam died Wednesday when the Yemen-based Houthis attacked the bulk commodities vessel True Confidence in the Gulf of Aden. At least two other sailors were injured. 

The incident marks the first deaths of crew members in the militants’ campaign against commercial shipping in one of the world’s busiest waterways, and follows the recent sinking of another vessel.

It also raises questions about how much risk shipowners are willing to accept while trying to keep their crews and cargoes safe. Most merchant vessels are already avoiding the region by sailing around Africa’s Cape of Good Hope.

“It is time for those shipowners who are continuing to transit through the Red Sea to reassess the necessity of their decision considering recent events,” David Appleton, head of professional and technical at Nautilus, which represents more than 20,000 maritime workers, said in the group’s statement. “The utmost priority should be the safeguarding of the lives of seafarers.”

The Iran-backed Houthis escalated their attacks in November, first targeting vessels that they said had ties to Israel in protest against its military campaign in the Gaza Strip. More recently, the militants have widened the strikes following American and British military efforts to keep the shipping lanes open.

The attack on the True Confidence is the latest example that the US and UK efforts are doing little to restore peace to a region that is a hub for the transport of everything from agricultural products to oil and gas. 

The carrier’s 20-person crew was forced to abandon ship due to the strike and were taken to Djibouti by an Indian navy vessel. The damaged ship, which was hauling a cargo of steel products, was drifting well away from land while salvage efforts were underway.

Last month, the crew of the Rubymar also abandoned ship following a Houthi strike. It resulted in the first vessel sinking since the militants heightened their attacks. The ship was carrying fertilizer and fuel, adding to concerns about an environmental disaster.