BEIJING - Much of China was inundated by the worst rains of the year, testing the Three Gorges Dam's anti-flood capacity, even as over a million people suffered from serious drought, China media said Tuesday.

In northwest China's Shaanxi province, 21 were confirmed dead and 18 others were still missing in floods triggered by heavy downpours that began Saturday, the Xinhua news agency reported.

As of Tuesday morning, 660,000 people in Shaanxi had been affected, and over 38,000 had been evacuated, according to the agency.

More than 700 people have been killed by floods, landslides and lightning this year in China, according to Xinhua.

Meanwhile, the giant Three Gorges Dam across the Yangtze was put to its first serious test as the biggest flood crest of the year moved down China's longest river.

"Following 14 years of construction, the Three Gorges construction has now begun for the first time to fulfil its anti-flood functions," Xinhua said.

On Monday, the International Federation of Red Cross and Red Crescent Societies described this summer's inundations as "some of the worst flooding to hit the country in the last 10 years."

In 2005 more than 1,000 people were killed in China's annual flood season, while in 1998, 4,185 people lost their lives in the deadliest rainy season of the past decade.

The capital Beijing was also hit by the heaviest rainstorm this summer on Monday, causing serious delays at the city's international airport and stranding about 10,000 passengers.

Xinhua said the terminal building had become "a mess" by Monday night, with children and elderly sleeping on the floor and passengers furious with airline companies, which claimed they were unable to provide food and lodging.

Even as rain was wreaking havoc in Beijing, part of north and northeast China is enduring its worst drought in two decades, according to the China Meteorological Administration climate office.

In central China's Hunan province, sustained drought for the past four months had triggered a water crisis for 1.2 million people, Xinhua said.

China's largest city Shanghai is also sweltering through what is likely to become its hottest summer on record.

Struggling to understand the freak weather patterns, scientists are blaming global warming, an issue that is the focus of growing attention in the world's most populous country.