China's Three Gorges Dam, the world's largest hydro-electro project, opened again to tourists this week -- on the condition they don't bring canned drinks, video camera or, bizarrely, umbrellas.

And only 1,000 people are allowed on to the 185-metre (600-ft) dam a day and they can only stay for 20 minutes within a stretch of 500 square metres above the floodgates, Xinhua news agency said.

The 2,235-metre-long dam in the central province of Hubei opened to tourists for the first time in 2005, from July to September -- the Yangtze River's main flood season when a spectacular flood discharge is on display.

But authorities opened the tourists' floodgates early this year because the dam's expected completion in May would bring more "selling points" for tourism, Xinhua said.

The security checks as strict as those at airports had ensured zero accidents during last year's opening season when the dam received 100,000 tourists, Xinhua said.

But it did not explain the ban on video cameras and canned drinks, let alone the umbrellas.

The project, which was launched in 1993 amid controversy over the relocation of about 1 million people and environmental damage, will have a generating capacity of 18.2 million kilowatt hours, easing a energy-starved China's power crunch.