"Once again, I am appalled at the fact that seafarers going about their work continue to be targeted and injured," he said. "I am truly saddened to learn that one crew member is currently unaccounted for on merchant vessel TUTOR following an attack on the ship in the Red Sea."

"My thoughts and those of IMO are with the family of the crew member.   

I strongly condemn any type of attack against international shipping, regardless of its motivation or cause," he added.

"I demand all governments and relevant organizations to provide maximum assistance to seafarers affected and to spare no effort in finding a resolution to this crisis," the IMO chief further said.

Dominguez noted that this situation cannot go on.

"Everybody is going to feel the negative effect if international shipping is not able to trade as normal. But our commitment is, above all, safeguarding the safety of all seafarers," he added.

An update from the United Kingdom Maritime Trade Operations (UKMTO) office on Tuesday said that military authorities reported seeing debris and oil in the Tutor's last known location.

"The vessel is believed to have sunk in position 14’19’N 041’14’E," it said.

The Greek-owned bulk carrier flying the Liberian flag was first hit in the rear by an unmanned small craft on June 12 while sailing in the Southern Red Sea. Later, the vessel was hit for the second time by an unknown airborne projectile.

This incident marked the first successful use of an unmanned surface vessel by the Houthis in their attacks.