Attacks in Red Sea shipping lanes have to stop otherwise international action will be taken, British foreign secretary David Cameron said on Thursday.
When asked, Cameron declined to specify what action Britain would take.
"This is illegal. It's not to do with Gaza, it's not to do with Israel. This is about the freedom of navigation. This is about the ability of ships to carry their cargo," he told reporters during a trip to Kosovo.
"The world economy, every economy, will suffer if ships keep coming under attack in this illegal and unacceptable way. And these attacks need to stop, or actions will be taken."