Six small craft approached a merchant vessel about 50 nautical miles from the Yemeni city of Mocha on Saturday before leaving the area, the United Kingdom Maritime Trade Operations (UKMTO) organization said, Paralel.Az reports citing Reuters.

Yemen's Iranian-backed Houthi militants have stepped up attacks on commercial vessels in the Red Sea in protest against Israel's war in Gaza. Various shipping lines have suspended operations, instead taking the longer journey around Africa.

"The vessel and crew were reported safe," UKMTO added in an advisory note on the incident.

The Houthis have vowed to continue attacks until Israel halts the conflict in Gaza, and warned that it would attack U.S. warships if the militia group itself was targeted.