Lesbos, Greece

Update (September 18, 2:27 p.m. EDT): Holland America is the latest cruise line to pull ships out of Lesbos. Nieuw Amsterdam's September 25 sailing will replace the call with Mykonos, and Rotterdam's October 24 sailing will visit Kusadasi instead. All pre-booked shore excursions will be refunded, the line said in a statement.

Update (September 11, 3 p.m. EDT.): Regent Seven Seas and Oceania Cruises have changed the rest of Lesbos stops for this fall. Seven Seas Mariner will replace its scheduled call in Mytilene on September 17 with a day at sea; on September 29, that stop will be replaced with Kavala, Greece. Kavala will also replace Seven Seas Voyager's scheduled call to Mytilene on October 29 and a stop there by Oceania Cruises' Nautica on October 6.

(4:05 p.m. EDT) -- Cruise lines that are scheduled to stop at Lesbos, a Greek island where thousands of migrants and refugees have arrived, have changed their itineraries.

On Sunday, Regent Seven Seas altered the itinerary for Seven Seas Mariner, replacing a call at Mytilene with a day at sea. Oceania's Riviera, which was also scheduled to stop today at Lesbos, replaced the port visit with Kavala, Greece.

"As for future sailings, we continue to monitor the situation and will make future itinerary adjustments, should the need warrant," spokesman Jason Lasecki said.

Silversea has also rescheduled its Lesbos stop for September 26. Silver Spirit will stop in Myrina, Lemnos, instead.

As many as 20,000 migrants from the Middle East and Africa are currently living in refugee camps on Lesbos, a Greek island that is only six miles from the Turkish coast. The migrants, many of whom are looking to reach Northern Europe, have been stuck on the island as the Greek government struggles to register them before they continue their journey, according to the Wall Street Journal. This weekend, thousands of migrants left one of the camps and marched on Mytilene, burning trees and trash along the way. Clashes with police were also reported.

On the Cruise Critic message boards, cruise passengers booked on itineraries going to Lesbos, as well as Turkey, have reported concern about the migrant situation. "It looks like a very sad and chaotic time there. Sitting on a cruise ship eating and drinking in excess as we sailed past ... people fleeing a war would really make me feel rotten," noted hypercafe.

On a separate thread, islandhalls, currently on Regent's Seven Seas Mariner, said: "We were in the Observation Lounge while we were sailing away and there was a small boat approaching Lesbos and filled with people, most agreed it was more refugees. I felt so ... sad and uncomfortable being in such luxury. My husband and I agree we will find an appropriate charity to donate [to] on our return home."

--By Chris Gray Faust, Senior Editor