Leading industry groups warned on Wednesday that urgent action was needed to stop the Houthis' attacks against merchant ships in the Red Sea, following the sinking a second vessel.

In November, Houthi militants aligned with Iran launched the first drone and missile attacks on this important trade route. They claimed to be doing so in solidarity with Palestinians living in Gaza. In over 70 attacks, the Houthi militants have also captured a vessel and its crew as well as killed at least 3 seafarers.

In a statement, the top shipping associations in the world said: "It's deplorable to see innocent seafarers attacked for doing their job, which is vital and keeps the world warm, clothed, and fed."

These attacks must cease immediately. "We call on states that have influence in the area to protect our innocent seafarers, and for a swift de-escalation in the Red Sea."

Salvagers confirmed Wednesday that the Greek-owned Tutor, a coal carrier attacked last week by Yemeni Houthi militants on the Red Sea has sunk.

Sources claim that the vessel was hit by missiles and a remote-controlled boat laden with explosives.

The attacks on ships in the Red Sea have increased dramatically. International naval forces are deployed to provide primarily defensive support to ships still sailing across the Red Sea.

On Wednesday, insurance industry sources expressed concern about the Houthis' use of drone boats to attack.

One industry source stated that they are more dangerous and harder to defend as they hit the waterline.

"Missiles - to date- have mainly caused deck damage and superstructure (damage) on ships."

Munro Anderson is the head of operations for Vessel Protect (part of Pen Underwriting), a marine war-risk and insurance specialist. He said that there have been 10 Houthi attacks so far in June, compared to five in May. He added that "the first successful use by commercial shipping of an unmanned vessel presents a new challenge in an already complex environment."

Insurers said that the additional premiums paid for war risks when ships sail through the Red Sea had risen to around 0.7% in recent days, from around 1% at the beginning of this year.

The rate hikes are expected to be a result of the second ship sinking, and the resulting losses. Each voyage will cost an additional hundreds of thousands.

Stephen Cotton, general secretary of the International Transport Workers' Federation (the leading union for seafarers), said that the best way to safeguard seafarers is by diverting ships around southern Africa.

He added: "We also would welcome the proper escorts of ships and the shielding by naval forces of ships, which would reduce risks of ships being struck." (Reporting and editing by Kirsten Doovan; Jonathan Saul)