Istanbul Map

(3:30 p.m. EDT) -- Celebrity Cruises has canceled all overnight stops in Istanbul for the rest of the cruise season due to ongoing security concerns.

Three ships -- Celebrity Reflection, Celebrity Equinox and Celebrity Constellation -- and eight itineraries are affected.

Celebrity has already skipped overnights in Istanbul twice in the past few weeks. The latest move comes just four days after the United States government issued a Travel Warning for Turkey, stating "U.S. citizens traveling to or residing in Turkey should be alert to the potential for violence."

The first sailing to be affected is a 13-night cruise from Barcelona on Celebrity Equinox which departs today (Sep. 7). The itinerary remains the same until the end of the cruise which will include an extra sea day instead of an overnight in Istanbul, though it will finish in the city.

The other cruises and changes are:

• Four cruises on Celebrity Constellation: September 18 & 30 and October 12 & 23. This ship will depart Istanbul on the same day instead of overnighting, and then spend a day at sea, calling in at Crete the following day.

• Celebrity Equinox, September 19. This cruise will depart Istanbul on the 19th, instead of the 20th, and spend a day at sea. It will call in at the same ports, but will have some slightly later departure times from Ephesus, Mykonos and Athens.

• Celebrity Reflection, September 21 and October 12 sailings. This itinerary is significantly changed, with an overnight in Athens instead of Istanbul, as well as stops in Rhodes and Crete.

A statement from Celebrity stated: "Due to the security concerns taking place in Turkey, Celebrity Cruises has cancelled overnight stays in Istanbul. We appreciate our guests' understanding and cooperation, and looking forward to welcoming them aboard.

"We will continue to closely monitor the situation in Turkey and have been contacting guests and their travel agents modifications to their upcoming itineraries.

"The safety and security, of our guests and crew members is always foremost in our minds."

Celebrity's move follows that of Costa, which in August canceled all its stopovers in Istanbul for the rest of the season.

--By Adam Coulter, U.K. Editor