Tropical Cyclone Cook

(2:15 a.m. AET) -- An end of season cyclone formed over the South Pacific's Vanuatu islands has caused at least two cruise lines to reroute ships in the region.

Tropical Cyclone Cook has been graded a Category 3 storm -- with wind speeds reaching 75 kilometres per hour -- and is currently located southeast of New Caledonia.

Royal Caribbean's Voyager of the Seas -- which departed Sydney on April 6 on a 13-night South Pacific and Fiji voyage -- dropped a call to the Isles of Pines in New Caledonia on Monday in favour of a sea day to avoid the cyclone.

In a statement, the line said: "The remainder of the itinerary will proceed as scheduled and guests have been informed onboard of the itinerary change and the rationale for the change. As always, the safety of our passengers and crew remains our number one priority and we will keep them updated if there are any further changes."

Carnival Cruise Line's Carnival Spirit, which departed Sydney on April 7, has been forced to drop both ports that featured on its original seven-night Pacific Islands itinerary. The island of Noumea was dropped from Monday's schedule and replaced with a sea day, while the Isle of Pines has been dropped from today's schedule. The ship will instead call at Moreton Island off the coast of Queensland later today.

The cruise line added: "We do not take the decision to change a route lightly, but the safety and wellbeing of guests and crew are always our number one priority.  

"Our thoughts are with the residents of Vanuatu and New Caledonia at this time and we look forward to returning to their shores."

Cruise Critic is in contact with all cruise lines with ships in the region and will update this story if more cruise lines reroute ships.

The Pacific's cyclone season runs from November to April. If you're planning a cruise during hurricane season, read up on Pacific Hurricane Season Cruising.

--By Kerry Spencer, Editor, U.K.