China's Shenzhou-11 spacecraft returned to earth Friday, bringing home two astronauts from the rising power's longest-ever orbital mission, in a milestone for its vaulting ambitions.

China's state broadcaster CCTV showed the return capsule's separation from the Tiangong-2 space lab 393 kilometres (244 miles) above the earth, and its descent through the atmosphere to its landing on the grassland of Inner Mongolia in the country's north.

After it landed, ground personnel rushed to plant two flapping red flags beside the capsule while observers applauded in China's mission control.

CCTV later showed footage of Jing Haipeng and Chen Dong being carried out of the capsule and waving as staff wrapped them in blue blankets.

The manned space programme's commander in chief Zhang Youxia announced that the mission was a "complete success".

The men spent the 33-day mission orbiting the earth carrying out experiments including cultivating silkworms, growing lettuce, and testing brain activity.

The Tiangong-2 space lab, launched in September, is also running experiments on growing rice and thale cress.

Beijing is pouring billions into its space programme in a bid to catch up with the US and Europe.

It announced in April that it aims to send a spacecraft "around 2020" to orbit Mars, then land and deploy a rover to explore the Red Planet's surface.

In their last entry in a space diary published by the official Xinhua news agency, the astronauts wrote that they kept fit in space by doing somersaults and zero-gravity tai chi.

"At the end of a busy day, we have some free time before going to bed," they wrote. "We take selfies to have some personal record of this unforgettable journey, or just go to the window and quietly stare at that beautiful blue planet called Earth."

Beijing sees the military-run programme as a symbol of China's progress and a marker of its rising global stature.

The nation's first lunar rover was launched in late 2013, and while it was beset by mechanical troubles it far outlived its expected lifespan, finally shutting down only last month.

But so far China has largely replicated activities that the US and Soviet Union pioneered decades ago.

It intends to set up its own manned space station by 2022, and eventually put one of its citizens on the surface of the moon.

In an interview earlier this week, Jing told Xinhua that "even in the wilderness of space" the astronauts could "always feel the love from our motherland".