Yemen's Houthi militia attacked two Saudi Arabian oil tankers in a military operation, the group said on Thursday, and a Saudi news agency later confirmed one of the two vessels was ablaze after an assault while sailing in the Red Sea.The Encelia transmitted a distress call via VHF radio, reporting it had been struck by a missile while operating at the outer port limits of Saudi Arabia's Jizan. (Representational Photo/AFP)The Saudi Arabian state news agency SPA, citing an official source at the General Transport Authority, said an attack caused a fire on the bow of the tanker Encelia but all crew members were safe. SPA did not say who had targeted the vessel.Authorities have secured the vessel and its crew and taken measures to protect the marine environment, describing the attack as a violation of international law, SPA reported, citing the source.In their statement, the Houthis said they attacked two tankers, the Encelia and Layla, saying the vessels had violated a naval blockade imposed by the Iran-aligned group on Saudi Arabia in the Red Sea. The Houthis said they targeted the tankers with a number of ballistic and cruise missiles as well as drones.Watch | Fourth mystery ship 'attack' near Yemen: Who's behind fresh escalation? Houthis or...? | Iran,USAA maritime security source said earlier on Thursday that the Encelia had transmitted a distress call via VHF radio, reporting it had been struck by a missile while operating at the outer port limits of Saudi Arabia's Jizan, in the Red Sea, and was on fire.The British maritime risk-management group Vanguard also said the Saudi-flagged tanker Encelia was struck by an unknown projectile on its starboard side about 70 nautical miles (130 km) southwest of Saudi Arabia's Al Shuqaiq at 2000 GMT.The United Kingdom Maritime Trade Operations agency (UKMTO) also said it had received a report of an incident in the same area, saying the master of a tanker reported being struck by an unknown projectile that caused a fire onboard, which the crew were fighting. UKMTO said no casualties or environmental impact had been reported.It was not immediately clear whether the UKMTO report referred to the Encelia, though the location and details matched the Vanguard report.Vanguard said the Houthis had reportedly claimed the attack, as well as saying they had hit a second vessel, the Layla, which it said remained unconfirmed.Read more: How a blockade in Red Sea tightens Iran's grip on global energy supplies | ExplainedIn the same statement announcing their attack on the two tankers, the Houthis also said they had forced around 10 ships to retreat and return. Reuters could not immediately verify this account.Five tankers changed course in the Red Sea on Wednesday, with two signalling the Suez Canal as their new destination after the Houthis warned ships to avoid Saudi ports, ship-tracking data showed.