Houthi spokesperson Yahya Sarea identified the vessels as the MSC Clara and Norwegian-owned Swan Atlantic, and said the attacks were carried out after their crews failed to respond to calls from the group.

The Swan Atlantic's owner said the ship had been struck by an unidentified object but none of the crew was hurt.

The MSC Clara is a Panama-flagged vessel, according to LSEG data. Details of the attack on the vessel were not immediately known.

The Houthis say they have been attacking vessels in the Red Sea with links to Israel in protest at its military offensive against Hamas in Gaza, and have warned against sailing towards the area.

The attacks have caused concerns about the impact on the passage of oil, grain and other goods on what is an important global trade route, and have pushed up the cost of insuring and shipping goods through the Red Sea.

Soon after the latest attacks, London's insurance market widened the area in the Red Sea it deems as high risk.

Taiwan's Yang Ming Marine Transport Corporation said it would divert any of its ships sailing through the Red Sea or Gulf of Aden via the Cape of Good Hope for the next two weeks.

Norway-based oil tanker group Frontline said its vessels would also start avoiding passages through the Red Sea and the Gulf of Aden.

"War risk insurance premiums are on the rise naturally, but as vessels gets re-routed around Africa shipping supply will be tighter as cargoes travel longer. That would put rates under a strong upwards pressure," CEO Lars Barstad told Reuters.

The announcement followed decisions by two major freight firms including MSC, the world's biggest container shipping line, to avoid the Suez Canal in response to the attacks by Houthi forces, which control most of Yemen, a poor Arab state.

The Suez Canal shipping route, which leads to the Red Sea, is a vital waterway for global trade, used to transport energy and other goods between Europe and Asia, and elsewhere. The route saves on time and expense by avoiding having to navigate around the entire Africa continent.

ONBOARD FIRE

Confirming Monday's attack on the Swan Atlantic, U.S. officials told Reuters multiple projectiles had been launched from Houthi-controlled territory in Yemen.

All the ship's system were operating normally although the water tank had been damaged in the attack, said Oystein Elgan, chief executive of owner Inventor Chemical Tankers.

Inventor Chemical Tankers had no Israeli ties, Elgan said.

The vessel's operator, Uni-Tankers, said the attack had caused a small fire which the crew brought under control, and that the ship, carrying vegetable oils, continued to Reunion Island.

A British maritime authority said it had received a report of a vessel that "experienced an explosion" on its port side in an attack 24 nautical miles north west of Yemen's Mokha port.

The vessel and crew were reported safe, it said in an advisory. The incident described by the UKMTO advisory was similar to those of the attack on the Swan Atlantic.

The United Kingdom Maritime Trade Operations (UKMTO) authority said in a separate advisory it had received a report of a vessel 24 nautical miles southeast of Mokha as being approached by a craft with several armed personnel onboard.

Warning shots were fired from the vessel and the craft with the armed personnel on board changed course, the advisory said.

The UKMTO authority said in other advisories it had received reports of an incident 63 nautical miles northwest of Djibouti and another incident in the vicinity of the Bab Al Mandab strait, 30 nautical miles south of the port Mokha.

The Houthis have pledged to continue their attacks until Israel stops its assault, but said on Saturday that real steps to ease the humanitarian crisis in the Gaza Strip would contribute to "reducing the escalation". They also said that they were in Oman-mediated talks about its sea "operations".

That was the first indication that the militia group may be willing to de-escalate. The U.S. has said it is seeking an expanded coalition to protect ships in the Red Sea and to send a signal to the Houthis, who have also fired drones and missiles at Israel since it began its campaign in Gaza in response to the Hamas rampage in southern Israel on Oct. 7.

Norway's Shipowners' Association said it expected Norwegian and international authorities to come together as soon as possible to secure safe passage for civilian vessels.

Norway's foreign ministry said Oslo was evaluating whether to participate in the proposed U.S.-led maritime coalition.

(Reporting by Tala Ramadan and Ahmed Elimam in Dubai, Phil Stewart in Tel Aviv, Terje Solsvik in Oslo, Louise Rasmussen in Copenhagen, Mohamed Ghobari in Aden ; additional Paolo Laudani in Gdansk; Writing by Clauda Tanios and Alexander Cornwell; Editing by Gerry Doyle, Mark Heinrich, Christian Schmollinger and Timothy Heritage)

By Ahmed Elimam, Phil Stewart and Terje Solsvik