Media playback is unsupported on your device Media caption Stephen McDonell watches Shenzhou 11 blast off from China's launch base

China has launched two men into orbit in a project designed to develop its ability to explore space.

The astronauts took off from the Jiuquan Satellite Launch Centre in northern China.

They will dock with the experimental Tiangong 2 space lab and spend 30 days there, the longest stay in space by Chinese astronauts.

This and previous launches are seen as pointers to possible crewed missions to the Moon or Mars.

An earlier Tiangong - or Heavenly Palace - space station was decommissioned earlier this year after docking with three rockets.

The astronauts on this latest mission were Jing Haipeng, 49, who has already been to space twice, and 37-year-old Chen Dong.

The BBC's Stephen McDonell was at the Jiuquan Satellite Launch Centre to witness the take-off.

Image copyright AP Image caption The astronauts Jin Haipeng (R) and Chen Dong will spend 30 days in space

From a remote launching station in Inner Mongolia, I watched the rocket tear through the sky.

It will take the astronauts about two days to reach the orbiting laboratory where they will live for a month. They will spend this time analysing plant growth in space and giving themselves ultrasounds to scan their bodies' performance.

Only a handful of foreign journalists were allowed into the high-security base to view the launch. But why let any of us in?

Well for one this country is proud of its space programme. At a time when Beijing is being criticised for flexing its ever-growing muscles, especially in the South China Sea, this is something different.

China can portray itself not only as a powerful nation, but one which is contributing to the body of knowledge.

Along the road into the launch centre are several huge billboards featuring President Xi Jinping giving himself a little clap as a "Long March" rocket sends yet another team into space.

He knows that China's ambitions in the stars may play well overseas but that means nothing to him compared to the credit he can take for them back at home.

The spacecraft, Shenzhou-11, took off from at 07:30 local time on Monday (23:30 GMT), lifted by a Long March-2F rocket.

The astronauts will spend the next month conducting experiments on the Tiangong 2.

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In a pre-mission interview with online portal China News, Mr Jin said: "There is definitely some pressure with this mission. I've even been dreaming about it at night."

"I'm not thinking about the bouquets, the applause or the glory. What I've been thinking more about is whether I have grasped all the knowledge and skills, whether I have addressed the weak areas."

Image copyright AP Image caption The Shenzhou-11 took off from China's northern Gansu province on Monday morning

In a congratulatory statement to the astronauts carried by state media, President Xi Jinping said he hoped they "vigorously advance the spirit of space travel".

He added that the mission would "enable China to take larger and further steps in space exploration, and make new contributions to building up China as a space power".

China has poured significant funding and efforts into its space programme, and plans to launch at least 20 space missions this year.

Image copyright EPA Image caption China's space programme has been given heavy publicity

Image copyright AP Image caption Tiangong 2, a precursor to China's permanent space station, was launched in September

It is only the third country - after Russia and the US - to carry out its own crewed missions. In 2013 it successfully landed its un-crewed Yutu, or Jade Rabbit, rover on the Moon.

It was excluded from the International Space Station due to concerns over the military nature of its space ambitions.

China has since embarked on plans to create its own permanent space station, expanding Tiangong 2 over the next few years by sending up additional modules. It is expected to be fully operational by 2022.

Authorities said last month that its predecessor, Tiangong 1, was due to crash back to Earth in 2017.