Shenzhou VI, based on Soviet Soyuz technology, lifted off on a Long March 2F carrier rocket from Jiuquan Satellite Launch Center at 9:00 amfor a five-day mission, carrying air force pilots Fei Junlong and Nie Haisheng.

It entered a fixed orbit 21 minutes later.

Having two crew on board is a departure from October 2003, when Yang Liwei spent 21 hours on a solo odyssey -- a mission that made China only the third country after the United States and the former Soviet Union to send a man into space.

"I feel good," said Fei in his first transmission from the craft.

Fei, 40, and Nie, 41, were seen off at the launch pad by Premier Wen Jiabao, who said he believed "the astronauts will accomplish the glorious and sacred mission."

"The entire nation has waited, the entire world is watching the success of the Shenzhou VI manned space launch," he said, adding the "great achievement" would go down "in the annals of the history of the Chinese people."

Amid some concern that China could use space for military purposes, Wen said this was not the case.

"China's entering into the scientific experiment of space flight is entirely for peaceful purposes and is a contribution towards the human race's works in promoting science and peace," he said.

Other top leaders including President Hu Jintao and Vice President Zeng Qinglong watched the event at the Beijing Aerospace Command and Control Centre, Chinese mission control.

Snow was falling at the launch site shortly before lift-off but stopped at about the time the astronauts entered their craft, Xinhua news agency reported.

TV images later showed the two elite air force pilots comfortably flipping and reading flight books after going into space. This indicated they felt at ease and more comfortable than first Chinese astronaut Yang, who felt a strong tremor about two minutes after liftoff, Xinhua said.

Millions of Chinese are estimated to have been glued to their TV sets watching the historic moment.

The fact that Wednesday's mission carried two astronauts reflects the twin purposes of China's space program, which aims for both scientific gains and kudos at home and abroad.

"If you are two people, you can do more complicated and more sophisticated types of work and experimentation," said Joan Johnson-Freese, an expert on China's space program at the US Naval War College.

"Part of it is also prestige. Two people is harder than one person."

Shenzhou VI is expected to circle around the Earth for the next 119 hours, or nearly five days, before landing in the Inner Mongolian grasslands.

The craft is based on the robust and thoroughly tested Soviet design for the Soyuz vessel, and consists of three modules.

These include the orbital module where scientific experiments are carried out; the re-entry capsule where the astronauts will spend most of their time; and the service module, which contains fuel and air, solar panels and other technical gear.

Unlike Yang two years ago, the two astronauts will leave their capsule for lengthy experiments in the orbital module at the nose of the spacecraft.

"They'll do quite a lot of medical tests, they'll take blood tests, urine tests, and they will also work out what kind of space food works for them," said Brian Harvey, the Dublin-based author of a book on China's space ambitions.

"Because ultimately what they are planning is a space station... and to do that they will need to learn how to survive on longer missions."

The flight of Shenzhou VI will also be a thorough and comprehensive test of China's tracking network, which includes tracking stations as far away as Namibia and four tracking ships placed around the oceans of the world.

In Jiuquan city, several hours' drive away from the satellite launch center, a sense of local pride was clearly visible.

"Wishing a successful launch of Shenzhou VI," said a large red poster in front of one of the city's hotels.

"We're very happy about all this," said Ma Li, a teenage resident of Jiuquan city. "It's amazing that we Chinese gradually have the know-how to pull this kind of thing off."

All rights reserved. copyright 2018 Agence France-Presse. Sections of the information displayed on this page (dispatches, photographs, logos) are protected by intellectual property rights owned by Agence France-Presse. As a consequence, you may not copy, reproduce, modify, transmit, publish, display or in any way commercially exploit any of the content of this section without the prior written consent of Agence France-Presse.