Thousands of people toured Dubai's Expo 2020 on the opening day on Friday, braving hot temperatures as the Covid-delayed world fair finally opened its doors one year late.

Visitors strolled or rode electric bikes around the huge showground, which has been built from scratch at a cost of about $7 billion on Dubai's desert outskirts.

As temperatures touched 38 degrees Celsius (100 Fahrenheit), robot information systems buzzed down the shaded boulevards and formation jets plumed coloured smoke overhead.

Dubai, one of the UAE's seven emirates, is hoping to attract millions of visitors in a boost to its profile and standing during the six-month fair. 

Visitor numbers were not immediately available for day one, but crowds were light and attendance appeared respectable rather than busy.

"It is really a source of pride that Dubai is hosting an Expo, which means a global event," said Aysha Hussein, a 20-year-old student and Emirati citizen.

"We are all excited about the event."

One hundred and ninety-two countries have pavilions at the event, with rivals such as Israel and Palestine present as well as Qatar, which was blockaded by its Gulf neighbours for three and a half years until January.

"We were looking forward for today and the opening," said Sarah Cann, 34, a British podiatrist who lives in Dubai.

"We're looking forward to seeing some of the shows perhaps, tasting food, different food from different countries and just exploring."

Human rights criticism 

Some exhibitors are hoping Expo, set to be the most attended event since the pandemic, reflects a turning point in the global fight against the disease.

But coronavirus measures are highly visible, with masks mandatory and social distancing on site. Visitors must be vaccinated or hold a negative PCR test.

Reem Al Hashimy, the Expo 2020 director general and the United Arab Emirate's minister of state for international cooperation, said officials were keeping a close eye on the situation.

"We're doing what is scientifically possible to mitigate Covid impacts but also what is necessary for things to also move on,  so trying to thread that needle or create that balance is going to be something we will watch very carefully," she told AFP.

The UAE last month brushed off a European parliament resolution urging member states and businesses to boycott Expo over the country's human rights record.

But criticism continued on Friday, with campaign group Human Rights Watch hitting out at the detention of activists.

"Dozens of UAE peaceful domestic critics have been arrested, railroaded in blatantly unfair trials and condemned to many years in prison, simply for trying to express their ideas on governance and human rights," said HRW's deputy Middle East director, Michael Page.

"Expo 2020 is yet another opportunity for the UAE to falsely present itself on the world stage as open, tolerant, and rights-respecting while shutting down the space for politics, public discourse, and activism."