Parents hold photos of their dead children as they walk through the ruins of the Fuxin No. 2 Primary School in Wufu, in China's southwest Sichuan province, Friday. (Greg Baker/Associated Press)

The death toll from the devastating earthquake in central China could rise as high as 80,000 "or more," Premier Wen Jiabao said Saturday, a drastic increase from the previous estimate of more than 55,000 fatalities.

Wen said fatalities "may further climb to a level of 70,000, 80,000 or more," according to the Associated Press.

Wen's comments came as he and UN Secretary General Ban Ki-moon visited Yingxiu, a town near the epicentre of the May 12 quake. The UN chief arrived in China from Burma, where he called on the country's reclusive military leaders to allow foreign aid workers to help cyclone victims.

More than five million people have been left homeless by China's quake, which reduced much of Sichuan province's buildings and infrastructure to rubble.

Lakes, radiation pose new threat

Officials in Beijing said nearly 25,000 people were confirmed as missing and close to 300,000 injured, but the number of victims was sure to go up as soldiers and rescue workers still hadn't reached the most remote mountainous areas in the quake zone.

Meanwhile, fears grew about possible flooding from dozens of lakes formed by landslides in the mountains above badly affected cities.

The Environmental Protection Ministry said experts from its National Nuclear Safety Administration were trying to contain 15 unspecified "sources" of radiation.

About 50 potential radiation sources had been buried by the quake, Environment Vice-Minister Wu Xiaoqing said Friday in Beijing. Although 35 have been secured, 15 remained buried under buildings and houses and despite being located were inaccessible, he said.

Xinhua news agency said 34 new lakes created when mudslides blocked rivers are rapidly growing in size and threatening to burst their banks.

Heavy monsoon rains could start falling in the central province of Sichuan soon, adding to fears of flooding and water contamination.

Tens of thousands of relief teams are deployed across central areas of Sichuan with the emphasis now on providing shelter and clean drinking water, and avoiding outbreaks of disease and infections.

Medical teams from China's Peoples' Liberation Army, as well as civilian doctors and nurses, have set up trauma camps, often in makeshift housing and under canvas.

With files from the Associated Press