Work has started on the construction of a fourth giant Oasis-class ship for Royal Caribbean International.

The first steel was cut for the vessel at the STX France shipyard in Saint-Nazaire, France, where the third Oasis-class ship also is being built.

The fourth Oasis ship is due to be delivered in 2018 following the introduction of the 5,000-plus passenger Oasis of the Seas (pictured) in 2008 and sister ship Allure of the Seas the following year.

Details of the two Oasis-class ships currently under construction will be revealed in the coming months, the line said

Allure of the Seas will be based in Barcelona for the first time this summer to operate in the Mediterranean.

Oasis of the Seas and Allure of the Seas currently sail alternating seven-night western and eastern Caribbean itineraries from Fort Lauderdale in Florida.

Meanwhile, Freedom of the Seas was showcase to 1,700 agents after the completion of a 24-day revamp in dry dock in the Bahamas.

An additional 67 cabins staterooms have been added to the ship, including a new category of panoramic ocean view accommodation located at the front of the ship featuring a floor-to-ceiling and wall-to-wall window.