The Shenzhou-23 crew aboard China's Tiangong space station sent heartfelt Mid-Autumn Festival greetings via a video from 400 km above Earth on Friday.

This is the fourth Mid-Autumn Festival since the completion of China's space station.

"Though the Earth is far away, our hearts are always beating in sync with our motherland and closely connected with the people of our country," said the commander Zhu Yangzhu.

Zhu, who is now on his second space journey, is the first commander among China's third batch of astronauts. This also marks the second time that he is spending the Mid-Autumn Festival in space.

"Dear family members, if you see a shining 'star' streaking across the night skies, that is our Tiangong, and it is me who misses you," said astronaut Zhang Zhiyuan, who is undertaking his first space flight journey.

The Mid-Autumn Festival, or the Moon Festival, is one of the most important traditional Chinese festivals, for family reunion and happiness with the full moon.

China's space station, Tiangong, means the Heavenly Palace.

Li Jiaying, or Lai Ka-ying in Cantonese, is the country's first astronaut from the Hong Kong Special Administrative Region, also the first payload expert flying into space among the fourth batch of astronauts.

"This is a special Mid-Autumn Festival. Through the porthole, what I miss most is the lights of thousands of homes across China, and what I yearn for most is the full moon that illuminates Hong Kong," said the female astronaut.

"Gazing at the bright moon in the skies, we share the beauty of the moon even though we are thousands of miles apart. At this moment, we yearn for it even more," she said.

The three astronauts were launched aboard the Shenzhou-23 spacecraft on May 24 this year, and then entered the space station Tiangong on May 25. To date, they have been working in orbit for four months.

"May our great motherland be prosperous and strong, and may our people be at peace. Wishing everyone a happy Mid-Autumn Festival and a happy family," said the three astronauts in the video from the space.