Saudi forces on Tuesday destroyed an explosive-laden boat off the coast of the Red Sea port of Yanbu, the defence ministry said.

"A bomb-laden unmanned (vessel) was intercepted and destroyed this morning," the ministry said in a statement, published by the official Saudi Press Agency. 

"Naval units were able to detect and monitor the activity of the bomb-laden (boat) in the Red Sea waters off the shores of Yanbu."

No group has so far claimed responsibility for the incident, which the ministry said was under investigation.

The incident comes as fighting escalates in neighbouring Yemen between Saudi-backed government forces and Iran-aligned Huthi rebels.

Yanbu, 860 kilometres (535 miles) east of the Saudi capital Riyadh, lies some 975 kilometres north of Saudi's frontier with Yemen.

Huthi insurgents are ramping up a bloody offensive to seize the oil-rich Marib region, the Yemeni government's last stronghold in northern Yemen.

The Huthis, who are battling the Saudi-led military coalition that intervened in Yemen's war in 2015, have also stepped up drone and missile strikes on Saudi targets, including its oil facilities.

The rebels have used bomb-rigged boats in the past to target the kingdom.

Last week, Greece said it will transfer a Patriot missile battery to Saudi Arabia to protect its critical energy infrastructure, as the Gulf kingdom grapples with the growing attacks.

Maritime security firm Dryad Global said it had received reports that a ship had been "attacked" off Yanbu.

But the firm later said the ship was "not involved in the incident" and it will continue to investigate.