Washington: US National Security Council Coordinator for Strategic Communications, John Kirby, on Thursday said the attacks on merchant ships by Houthi rebels needed to stop.

Vowing all steps to stop such attacks, Kirby added that more than twenty countries are in the process of joining the US under 'Operation Prosperity Guardian' to protect shipping assets from such attacks.

"We take seriously the responsibility to protect our ships and our sailors at sea, as well as the responsibility to protect the flow of international commerce...I would add that we're not the only ones. Other nations are joining us in that effort. Some 20+ nations now are involved in the operation Prosperity Guardian. These attacks need to stop, and we're going to do what we have to do to continue to protect that shipping, to protect our sailors," Kirby said.

Operation Prosperity Guardian is a US-led military operation by a multinational coalition formed in December 2023 to respond to Houthi-led attacks on shipping in the Red Sea.

Kirby also condemned the seizure of an oil tanker by the Iranian navy and sought the immediate release of the ship, along with the crew.

"We condemn this apparent seizure, Iranian government should immediately release the ship and its crew. It is an unacceptable action that needs to stop. We continue to work with our allies and partners to deter Iran's full range of concerning and destabilising behaviour in close coordination with the international community," he said.

Earlier, on Thursday, Iran seized a tanker with Iraqi crude destined for Turkey in retaliation for the confiscation last year of the same vessel and its oil by the United States, Al Jazeera reported, quoting the Iranian state media.

"The Navy of the Islamic Republic of Iran seized an American oil tanker in the waters of the Gulf of Oman in accordance with a court order," the state-run IRNA news agency said.

"After the theft of Iranian oil by the United States last year, St Nikolas tanker was seized by Iran's Navy," the force said in a statement.

According to Al Jazeera, the seizure comes after weeks of attacks by Yemen's Iranian-aligned Houthis on vessels in the Red Sea. The Houthi rebels say they are carrying out the attacks in solidarity with Palestinians in Gaza amid Israel's assault on the territory.

The attacks by armed Houthi rebels have raised the risk of possible retaliatory strikes from US-led forces patrolling the busy waterway, especially after a United Nations Security Council vote on Wednesday condemning the Houthis.

But while the Houthis have been concentrated on the Bab al-Mandab Strait, to the southwest of the Arabian Peninsula, Thursday's incident was located closer to the Strait of Hormuz, between Oman and Iran.

The British maritime security firm Ambrey said the incident began at about 7:30 a.m. (03:30 GMT) when several armed men boarded the Marshall Islands-flagged St Nikolas, around 50 nautical miles east of Sohar in Oman, and then headed towards Bandar-e-Jask in Iran.

TankerTrackers.com, which tracks and reports global shipments of crude oil, said the tanker was carrying "Iraqi oil" and previously went by the name Suez Rajan, Al Jazeera reported.

Ambrey said the recently renamed tanker was previously prosecuted and fined for carrying sanctioned Iranian oil, which was confiscated by US authorities. The yearlong dispute ended with the US Department of Justice seizing one million barrels of Iranian crude.