Expo 2020 Dubai, a major world fair that opened last week, on Sunday said three workers on the project had died after contracting COVID-19, revising up the number of fatalities since 2015 to six workers.

The organiser had for the first time on Saturday disclosed three work-related deaths and 72 serious injuries among 200,000 workers during construction of the site, defending the accident rate as less than half of that of building work in Britain.

"Unfortunately we had three worker related deaths due to Covid. That was during the course of the pandemic," Expo representative Sconaid McGeachin told a daily briefing. McGeachin said the three deaths disclosed earlier were construction-related.

She referred reporters to local authorities for comment on how many Expo workers had so far caught COVID-19. The Dubai government media office did not immediately respond to an emailed Reuters request for comment.

The United Arab Emirates does not give a breakdown for COVID-19 cases and deaths for each emirate, including regional trade and tourism hub Dubai.

Huge projects in the Gulf region such as the Expo, and Qatar's preparations for hosting the 2022 FIFA soccer World Cup, have faced international scrutiny, with rights groups criticising conditions for low-paid migrant workers. Overcrowding in worker accommodation was one of the main factors causing a surge of infections in the United Arab Emirates and other Gulf states at the start of the pandemic.

The country has rolled out one of the world's fastest vaccination campaigns, with more than 80% of the population of some 10 million people inoculated. The UAE is betting the six-month Expo will attract 25 million visits.

Visitors entering aged 18 and over must show proof of vaccination or a negative COVID-19 test. There are also testing facilities on site.