Spain briefly closed the airspace over the north-eastern region of Catalonia and three other regions as remnants of an out of control Chinese rocket passed by before hitting the ocean off Mexico's coast.

Authorities said the airspace closure, which encompasses Barcelona, caused delays to about 300 flights. 

"Due to the risk associated with the passage of the space object CZ-5B through the Spanish airspace, flights have been totally restricted from 9:38am to 10:18am (local time) in Catalonia and other communities," Catalonia's emergency service said on its Twitter account.

China Manned Space agency said remnants from China's most powerful rocket, the Long March 5B, re-entered the atmosphere at 6:08 pm Beijing time, with most of them burning up and the rest touching down in the Pacific Ocean with coordinates 101.9 degrees west, 9.9 degrees north.

That is almost 1,000 kilometres south-west of Acapulco in Mexico.

The rocket blasted off on October 31 from southern China to deliver the last module of the Chinese space station.

It was the fourth flight of the Long March 5B since its maiden launch in May 2020.

On its first deployment, fragments of the rocket's boosters landed on the Ivory Coast, damaging several buildings in the West African nation, though no injuries were reported.

Debris from the second flight landed harmlessly in the Indian Ocean, while remnants from the third fell into the Sulu Sea in the Philippines.

A rocket's re-entry into the atmosphere is a common international practice, Chinese foreign ministry spokesperson Zhao Lijian said. 

Mr Zhao said the probability of causing harm to aviation activities and the ground was "extremely low".

Reuters