Singapore hopes to start "cruises to nowhere" in a bid to revive its coronavirus-hit tourism industry, but critics warned Monday against a risky move that could spark Covid-19 outbreaks.

The global cruise industry has largely ground to halt due to virus-related travel restrictions, and following a series of outbreaks on packed vessels. But the tourism board in Singapore, a key port and transport hub in Asia, is holding talks with cruise lines on putting on voyages that depart from and return to the city-state.

Officials will put in place "appropriate measures that will enable cruises to resume in a safe manner," the board's cruise director Annie Chang told AFP. She did not say when the cruises might start. However, Marcie Keever, oceans and vessels programme director at Friends of the Earth, warned about "the potential to have Covid outbreaks" on cruise liners. "The cruise industry was a large contributor to Covid outbreaks in several ports around the world," she told AFP.

She also warned about the environmental impact of restarting cruises. Last week, Singapore Airlines ditched a plan to launch "flights to nowhere" to boost its virus-hit finances following an outcry over the impact on the climate.

Several cruise lines worldwide, including Britain's P&O Cruises and Norway's Hurtigruten, have cancelled all sailings for now due to travel restrictions. Singapore saw virus outbreaks in crowded dormitories housing low-paid migrant workers, but they have now largely been brought under control.