"Clearly it is unsafe for anyone to go there.”
Others set to travel said they would not to be cowed into cancelling.
"Not giving in to terror. We want to support you in your time of need. Never gave any thought about cancelling our trip,” Facebook user John Karmouche said in a post.
Named by the Lonely Planet guide for independent travellers as the best country to visit in 2019, Sri Lanka had rebuilt its image as a tropical paradise after crushing a long-running separatist insurgency by ethnic minority Tamils a decade ago.
Arrivals of 2.3 million last year were up by more than 400 percent on 2009 levels, according Sri Lanka Tourism Development Authority data.
But the suicide bombers who killed at least 290 people, including 32 foreigners, and wounded 500 have in all likelihood ended the boom in tourism for some time.
Denmark's richest man, Anders Holch Povlsen, and his wife lost three of their four children in a blast at one of the hotels. A British mother and son were killed at a breakfast buffet and two Australians were also among the dead.
The industry was the third largest and fastest growing source of foreign currency, after private remittances and textile and garment exports, accounting for almost $4.4 billion or 4.9 percent of gross domestic product (GDP) in 2018.
"The attacks will not only impact already weak economic activity (real GDP growth was at a 17-year low of 3.2 percent in 2018), but also the country’s relatively vulnerable external liquidity position," Citi Asia Economics said in a note that warned the hardest blow would fall on tourism.
The U.S. State Department said in a revised travel advisory of the danger of "terrorist groups" plotting more attacks. Targets could include tourist locations, transport hubs, shopping malls, hotels, places of worship and airports.
Other governments, including Japan and Australia, have also cautioned citizens planning travel to Sri Lanka.
Prime Minister Scott Morrison told Australians "reconsider your need to travel and avoid all affected areas".
JTB, Japan's largest travel agency, has waived cancellation charges, and modified its package tours leaving Japan before May 10 to avoid risky locations, like Colombo, and will decide later on tours leaving after May 11, a spokeswoman said.
Two major airlines in neighbouring India, state-owned Air India and the largest carrier Indigo, owned by Interglobe Aviation INGL.NS , said they would waive rescheduling and cancellation charges for travel scheduled before April 24.
India was the single largest source of visitors last year, with 425,000, while 266,000 came from China, Sri Lanka's newfound friend, and more than 254,000 from old colonial power Britain.
Visitors come for the glorious vistas across the forests in the national parks, the surf crashing on sandy beaches, verdant tea plantations, Buddhist temples and charming old colonial towns.
The government's latest tourism campaign celebrates the island's charms with the simple slogan 'So Sri Lanka'.
After Sunday's outrage it could become a lament.
(Reporting by Lidia Kelly in MELBOURNE, Kiyoshi Takenaka and Linda Sieg in TOKYO, Nivedita Bhattacharjee in Bengaluru and Euan Rocha and Sankalp Phartiyal in MUMBAI, and Aditi Shah in NEW DELHI Writing by Simon Cameron-Moore Editing by Robert Birsel ) ((firstname.lastname@example.org; +90 212 350 7027; Reuters Messaging: email@example.com))