Two Carnival Corp & plc units, P&O Cruises and Cunard Line, are reported to have cancelled all their Black Sea port visits in 2015, Cruise Critic says on its website.

"A total of 13 cruises are affected by the decision -- two of them on P&O Cruises' ships and the others on Cunard Line's Queen Victoria. The ships will go as far as Istanbul then turn round, rather than go into the Black Sea itself," the report said..

The cruises affected are:

• P&O's Arcadia, August 26 to September 20, 2015.

• P&O's Adonia, September 7 to October 7, 2015.

• All Queen Victoria's July to October cruises.

Since March eight cruise lines -- including Azamara Club Cruises, Oceania, Regent Seven Seas, Silversea and Windstar -- have canceled Ukraine port stops, replacing them with calls in Turkey, Romania, Georgia and Bulgaria. Some sailings also spent more time in Greece, Cruise Critic said.