President Xi Jinping declared the 19th Asian Games open at a colourful ceremony in Hangzhou on Saturday, launching a two-week sporting extravaganza that boasts more athletes than the Olympics.

After being delayed by a year because of the Covid pandemic, more than 12,000 competitors from 45 nations and territories will battle it out in 40 sports.

In front of Syrian President Bashar al-Assad and other visiting leaders, President Xi officially opened the Games at the 80,000-capacity Hangzhou Olympic stadium, also known as "the Big Lotus."

International Olympic Committee president Thomas Bach was also among the dignitaries – and leaders from Cambodia, Kuwait and Nepal, among others, had all been expected to attend.

"Finally we can gather for the 19th Asian Games," Raja Randhir Singh, acting president of the Olympic Council of Asia, told the crowd to more cheers.

"The one-year postponement was unprecedented in OCA history," he added.

Security was tight in the area around the arena in the hours leading up to the ceremony, with roads closed and police stationed on street corners.

Spectators were given thorough security checks before entering and staff confiscated food and umbrellas. The light rainfall in recent days had stopped.

The theme of the ceremony was water and it also celebrated Hangzhou's ancient history and landscape, while also giving a nod to the city's reputation as the unofficial home of China's tech industry.

"I feel very happy and excited," a 35-year-old woman spectator surnamed Zhang said.

"I feel it's a great honour for the city."

North Korean athletes are contesting their first major international competition since the pandemic.

But the biggest cheer of all was reserved for hosts China, who are overwhelming favourites to top the medals table, with Japan and South Korea battling for second.

Games athletes will fight for medals in Olympic staples such as athletics, swimming, football, gymnastics and cycling.

ESports will make its debut as a medal event at the Games, in what is seen as a step towards inclusion one day in the Olympics.

There will also be regional specialities including dragon boat racing, the Chinese martial art wushu and kabaddi.

Nine sports, among them boxing, break dancing and tennis, will serve as Asia qualifiers for next year's Paris Olympics.

A sprinkling of world and Olympic champions adds some stardust, including India's javelin king Neeraj Chopra, Qatari high jumper Mutaz Essa Barshim and Chinese swimming stars Qin Haiyang and Zhang Yufei.

Olympic Council of Asia honorary life vice-president Wei Jizhong said having so many sporting disciplines was about giving opportunity to as many athletes as possible.

"We are open to all. This means our Games are not concentrated only for elite sportspeople," he said.

Although the Games officially opened on Saturday, sports such as football, cricket, volleyball and table tennis have already begun.

The Games will be staged at 54 venues – 14 newly constructed – mostly in Hangzhou but also extending to cities as far afield as Wenzhou, 300 kilometres south.

The Games in Hangzhou, a city of 12 million people an hour's bullet train from Shanghai, will showcase some of China's latest tech including robot dogs, driverless buses and facial recognition. (AFP)