Astronomers believe an "otherworldly'' light seen in the sky on Friday night is linked to a Chinese rocket launch hours earlier.

Tūhura Otago Museum director and astronomer Ian Griffin said the striking phenomenon appeared about 30 minutes after a rocket reportedly lifted off from China.

''As I understand it, there was a launch at about half past six our time,'' Griffin said.

''Roughly half an hour later, the rocket was passing over New Zealand when there was likely a stage separation or firing of rocket jets, and it became incredibly bright in the sky.''

Griffin said the launch of a Long March-2D rocket carrying experimental satellites reportedly took place from the Xichang Satellite Launch Center earlier that afternoon Beijing time.

Reports and images of a glowing cloud moving across the sky quickly surfaced on social media, with sightings spanning much of the country.

Griffin, who observed the event from Middlemarch near Dunedin, described it as ''a very bright cloud'' that slowly expanded as it…