UK maritime security reporting body UKMTO has issued a second warning in two days after an approach by suspicious boats to a merchant vessel in the Red Sea.
It said it had been told of an incident on 3 November in the Bab-el-Mandeb strait in which a ship saw two skiffs coming towards it.
The smaller boats contained four or five people each.
They approached to closer than a nautical mile, at which point a warning flare was fired.
Both skiffs then passed astern. One later began a second approach and a further warning flare was fired, which turned it away.
Vessel and crew are safe.
UKMTO said vessels transiting the area are advised to exercise extreme caution.
It had earlier warned of a similar incident in the area on 1 November.
An unnamed ship had been approached by three small vessels, again with four or five people on board.
