China on Thursday launched its riskiest space flight yet, sending three men into orbit on a mission that will include the nation's first ever space walk, state media said.

The Shenzhou VII spacecraft lifted off from Jiuquan Satellite Launch Centre in northwest China at 9:10 pm (1310 GMT) in the presence of President Hu Jintao and other senior leaders, state television reported live.

"The successful launch marked the first victory of the Shenzhou VII mission," a triumphant Hu said.

As the spacecraft entered its pre-set orbit, the three astronauts kept in contact with ground control, occasionally waving to a camera as notebooks floated around in the weightlessness of their shuttle cabin.

Hu earlier saw off the three, led by 41-year-old Zhai Zhigang, as they prepared for their 68-hour journey to space and back.

"I have come to send you off, to wish you success," Hu said in the televised meeting, carried out with the formality of an ancient Confucian ritual.

Zhai, an air force colonel who grew up in abject poverty in China's bleak northeast, is expected to carry out the 30-minute space walk either Friday or more likely Saturday, according to state media.

"We're determined to complete the manned space mission of Shenzhou VII," Zhai told Hu. "The motherland and the people can rest at ease."

The launch, a powerful symbol of China's emergence as a space power, came just before the 50th anniversary of the US National Aeronautics and Space Administration, or NASA, on October 1.

Getting comfortable with the art of spacewalking is a crucial next step in China's most immediate extra-terrestrial ambition: to build a permanent space lab.

By 2010 two more unmanned craft will have been sent up, as well as another manned spaceship with a crew of three to start work on the lab, according to the China Daily.

In Beijing, foreign ministry spokesman Liu Jianchao said the mission was part of China's effort to "explore and make peaceful use of outer space."

"We believe this will further promote our space flight technology and make a contribution to the peaceful use of outer space for all human beings. We wish the Shenzhou VII mission a complete success," he said.

The astronauts have trained together for more than a decade, but the mission is not without its risks, notably the space walk.

"The process of (space walks) cannot be simulated completely on the ground," said Wang Zhaoyao, spokesman of the manned space mission.

"Some of the newly developed products have to be tested in flight for the first time."

One of the astronauts -- government websites have said it will be Zhai -- will test a new Chinese-made spacesuit on the space walk.

Coming just a month after the end of the Beijing Olympics, the mission may trigger a new burst of nationalist pride in some segments of the population.

Space enthusiasts hoping to witness for themselves China's next bid for greatness have been converging on Jiuquan, a city of about 340,000 people, mostly farmers and miners, in a remote part of Gansu province.

For those who were not successful in reaching the launch site, a large TV screen was erected in downtown Jiuquan, but rain kept most people indoors.

"It was an incredible launch. China has done it again. I feel proud every time they launch a rocket. Zhai Zhigang is my hero," said 23-year-old Wang Jun.

For Wang Xiaoyue, a 29-year-old employee of the tourism industry, pride centred on her home town.

"I'm honoured to be from Jiuquan. People from all over China know my city, and people from all over the world know the city," she said.

China first sent a man into space in 2003, becoming the third nation after the United States and the former Soviet Union to accomplish the feat.

The country's second manned space mission in 2005 sent two men into orbit for 115 hours, with the task of studying living and working conditions in space.

China's manned space programme is characterised by its frugality compared with the US and Soviet programmes in the 1960s, and it does not repeat a test or an experiment that has already proved successful, observers say.

The Shenzhou VII is scheduled to land in the northern Inner Mongolia region after the mission is completed.