China began its longest manned space mission yet Tuesday with the launch of the Shenzhou-10, state television showed, as the country steps up an ambitious exploration programme symbolising its growing power.

The rocket ascended above the Jiuquan space centre in the Gobi Desert exactly on time at 0938 GMT, trailing a vast column of flame.

The three astronauts on board -- who include Wang Yaping, 33, China's second woman in space -- saluted cameras mounted inside their capsule.

A few minutes after launch the boosters detached from the rockets, and a little later the solar panels of the Shenzhou-10 -- the name means "Divine Vessel" -- were deployed, to applause from mission control.

"The vessel is already in orbit," said Zhang Youxia, the manned space programme's chief commander. "I now announce the launch was a great success."

The crew are due to spend 15 days in orbit, in a mission that is a crucial step towards China's goal of building a full space station capable of housing astronauts for extended periods.

President Xi Jinping, fresh from a summit with US President Barack Obama, was on hand to watch the departure.

Beijing sees the multi-billion-dollar space programme as a marker of its rising global stature and mounting technical expertise, as well as the ruling Communist Party's success in turning around the fortunes of the once poverty-stricken nation.

The project is heavily promoted to the domestic audience, and state broadcaster CCTV began continuous coverage several hours before the launch.

Xi told the trio he had come to see them off on behalf of the Communist Party, the government, the military and "all the nationalities and people of the entire nation".

"You make all the Chinese people feel proud. Your mission is both glorious and sacred," he added.

Mission commander Nie Haisheng responded: "We will certainly obey orders, comply with commands, be steady and calm, work with utmost care and perfectly complete the Shenzhou-10 mission."

State-run newspapers gave the mission blanket coverage, with stories and pictures of the astronauts on almost every front page.

Astronaut Wang will teach lessons to schoolchildren via video link from space, officials said.

"We are all students in facing the vast universe. We are looking forward to joining our young friends to learn and explore the mystical and beautiful universe," she told a press conference on Monday.

In a profile of Wang, the official Xinhua news agency said she trained as a transport pilot in the air force and has 1,600 hours of flying experience, including dispelling clouds for the opening ceremony of the Beijing Olympics in 2008.

She is a major in the military and a member of the Communist Party.

"The experience of doing farm work since an early age has made her strong, and the habit of long-distance running tempered her will," Xinhua said.

It quoted her as saying that during parachute exercises in the air force: "We girls all cried while singing an inspiring song 'A Hero Never Dies' on our way back after the training."

The third crew member, senior colonel Zhang Xiaoguang, has previously tried for selection for space missions but was not picked, Xinhua said.

"If success is part of our life, so are setbacks. If those who had never failed are winners, so are those who always keep on trying," it quoted him as saying.

The Shenzhou-10 will dock with the Tiangong-1 -- "Heavenly Palace" -- space laboratory, and the crew will transfer into it and carry out medical and space technology experiments.

China first sent a human into space only in 2003 and its capabilities still lag behind the US and Russia. But its programme is highly ambitious and includes plans to land a man on the moon and build a station orbiting Earth by 2020.

At the same time the US, long the leader in the field, has scaled back some of its projects, such as retiring its space shuttle fleet.

Independent space analyst Morris Jones, who is based in Sydney, Australia, told AFP it was "a very smooth and clean launch".

"My expectation is that they will continue to grow their programme at a steady pace, so it will get larger in the next decade and they will probably mount a serious challenge to the Americans and everyone else in space."