The global shipping industry sounded the alarm this week about the safety of merchant vessels operating in the Red Sea after a second ship was sunk by Yemen’s Iranian-backed Houthi rebels earlier this week.

In a statement, several international maritime organizations called for action against the regular Houthi attacks that “directly contravene the fundamental principle of freedom of navigation.”

The M/V Tutor, a Liberian-flagged, Greek-owned bulk cargo carrier ship took on water and sank several days after the Houthis attacked it on June 12 with a radio-controlled fishing boat packed with explosives. A crew member aboard the ship is believed to have been killed, officials said.

“This is an unacceptable situation, and these attacks must stop now. We call on states with influence in the region to safeguard our innocent seafarers and for the swift de-escalation of the situation in the Red Sea,” read the statement released Wednesday by the International Association of Dry Cargo Shipowners, the International Association of Independent Tanker Owners, the World Shipping Council, the International Chamber of Shipping, and several other maritime organizations.

In March, the Houthis attacked the M/V Rubymar, a Belize-flagged cargo ship carrying fertilizer. It sank in the Red Sea after taking on water for days after the strike.

“We have heard the condemnation and appreciate the words of support, but we urgently seek action to stop the unlawful attacks on these vital workers and this vital industry,” the commercial shipping organizations said in their statement.

The Houthis claim their targets are vessels bound for Israeli ports or those owned or operated by Israeli companies. They later expanded their target list to include U.S. and British commercial ships. The Houthis began their attacks in the vital maritime trade corridor after Israel launched its war in the Gaza Strip against Hamas, which perpetrated an Oct. 7 attack on Israel that killed more than 1,200 people.

The Houthis fired missiles at another ship, the M/V Verbena, a day after the Tutor was attacked. The crew of the Ukrainian-owned and Polish-operated bulk cargo carrier was forced to abandon the vessel after they were unable to control fires on board. At least one crew member was seriously injured in the incident, officials said.

“It is deplorable that innocent seafarers are being attacked while simply performing their jobs, vital jobs which keep the world war, fed, and clothed,” the shipping industry statement said.

The Houthis have launched dozens of strikes, mostly using missiles and drones, that are believed to have killed four merchant sailors. At least 15% of the world’s maritime trade passes through the Red Sea corridor. The U.S. Defense Intelligence Agency said vessel traffic in the region has declined by 90% since the attacks began.

The maritime attacks by the Houthi rebels appear to be escalating even as the U.S. maintains a robust naval presence in the Red Sea. The Navy launched Operation Prosperity Guardian in response to the Houthi-led attacks on commercial ships.

“This continued malign and reckless behavior by the Iranian-backed Houthis threatens regional stability and endangers the lives of mariners across the Red Sea,” U.S. Central Command said in a statement. “The Houthis claim to be acting on behalf of Palestinians in Gaza and yet they are targeting and threatening the lives of third-country nationals who have nothing to do with the conflict in Gaza.”