Egypt experienced its bloodiest day since the revolution on Wednesday when some 278 people were killed in a deadly operation to break up protest camps in Cairo.  As the country teetered on the brink of civil war on Thursday, several nations issued a fresh round of travel warnings advising citizens to steer clear of Cairo and the Luxor Valley, and remain extremely cautious in the popular Red Sea resorts of Dahab, Marsa Alam, Taba, Nuweiba and Sharm el-Sheikh.

Tour operators, meanwhile, said they were closely monitoring the situation and providing updates for both prospective travelers and those already in the country. Citizens of the U.K. represent one of Egypt’s biggest visitor groups, and the Association of British Travel Agents estimated that there were about 20,000 British holidaymakers in the country this week. Thomson and First Choice, Britain’s two largest tour operators, had a combined 9,000 clients in Egypt on Wednesday, 8,500 of whom were in the Red Sea resort of Sharm el-Sheikh.

“Following the reported demonstrations in Cairo and other locations, the Foreign and Commonwealth Office is advising against all but essential travel to Cairo, Alexandria, Luxor and Suez.  It is not currently advising British nationals to leave the country, and the advice has not changed for Sharm el-Sheikh, Hurghada, Taba and Marsa Alam,” the companies, which are both owned by TUI Travel PLC, said in a joint statement.

“Sharm el-Sheikh is a considerable distance -- indeed, an eight hour drive -- from Cairo.  There have been no related incidents in Sharm el-Sheikh or any other popular Red Sea tourist resort areas,” the companies said.

The tour operators called Sharm el-Sheikh “a country in itself” that runs separately from the rest of Egypt and benefits from having just one secure road in and a low crime rate. Thomson, First Choice, Kuoni, Discover Egypt and others have all canceled holidays to other parts of the country pending advice from the Foreign Office.

The U.S. Department of State, meanwhile, issued a travel warning for Egypt last month urging U.S. citizens to defer travel until further notice. It also asked citizens living in Egypt to depart because of the political and social unrest.

The U.S. Embassy in Cairo temporarily closed to the public on Thursday and suspended regular consular services. “U.S. citizens are advised to maintain valid travel documents and enroll with the Department of State or the U.S. Embassy Cairo through the State Department’s Smart Traveler Enrollment Program website,” the embassy said in a statement.  “If you enroll we can keep you up to date with important safety and security announcements and can also help your family and friends get in touch with you in an emergency.”

Canada also closed its embassy in Cairo until further notice and updated its travel warning for Egypt on Wednesday, advising against travel beyond Red Sea coastal resorts, where citizens were told to “exercise a high degree of caution, due to the unpredictable security situation and continued demonstrations throughout the country.”

Ireland, Finland, Australia, and the United Arab Emirates, among others, all updated their travel warnings for Egypt following the violent crackdown on protesters gathered outside the Raba'a al-Adawiya mosque on Wednesday.

Cairo Airport and its transit operations were operating normally on Thursday, though several airlines axed flights and others reportedly arrived with less than 50 percent occupancy. Egyptian flag-carrier EgyptAir issued a statement on Wednesday, saying that all international and domestic flights would operate as scheduled with no planned cancellations.

“All EgyptAir passengers are kindly requested to proceed to the airport at least three hours before the scheduled departure time of their flights; evening and early morning flights will be available for check-in before the start of curfew, yet in case of heading to the airport during curfew time, please make sure to have all necessary travel documents in hand to be presented at any security check point,” the airline said.

On its Facebook page, the carrier added that Cairo Airport would provide passengers arriving during the state of emergency curfew with a hotel room to stay in until 6 a.m.

Egyptian ports remained open on Thursday, though most cruise ships have canceled their calls amid the instability. Costa Cruises announced this week that it would pull out of Egypt entirely for its autumn and winter 2013-2014 season. The company said it would restore calls to Egyptian ports as soon as the cruise line could ensure the safety and security of its guests.

Last month, Thomson canceled all forthcoming calls in Port Said and Alexandria, while Discover Egypt canceled its Nile River cruises. Holland America Line, Princess Cruises, MSC Cruises, Seabourn and German cruise line AIDA also began nixing stops in Egypt last month, including Sharm el-Sheikh.

According to industry website Cruise Critic, Elhamy Elzayat, chairman of the Egypt Tourism Federation, has written to tour operators stating: “Until a new cabinet is appointed I will personally work with my colleagues members of the Tourism Federation Board together with the chairman of the tourism promotion board to put a plan of action to recreate confidence in the Egyptian tourism product bringing on board as soon as appointed the Ministers of Tourism, Antiquities, Culture, Interior and all appropriate governors to create a new image for Egypt.”

Elzayat estimated that Egypt’s tourism industry had suffered losses totaling about $720 million since the military coup last month, because of a decline in hotel bookings and package holidays. The number of tourist arrivals in July fell by about 37 percent, with hotels in Luxor and Aswan reporting just 15 percent occupancy.