Two Chinese men involved in a brawl that forced their Swiss Air flight to make a U-turn and return to Zurich have been released from custody, a Swiss prosecutor told the Xinhua News Agency Tuesday.

"They were released on Monday local time," the prosecutor said, adding that the 57-year-old Chinese passenger was ordered to pay a fine daily for 90 days on the charge of undermining the safety of public transport.

Consul Wu Tengfei from the Chinese consulate general in Switzerland told the Global Times that he had contacted Zurich police to offer assistance to the two citizens as soon as he heard of the incident.

The older passenger is accused of slapping a 29-year-old man, who had refused to put his seat upright while a meal was being served. After being slapped on the head the younger man jumped to his feet and pushed the older man.

Passenger Valerie Sprenger, 39, told the Swiss newspaper Blitz that the older man attacked the young man after the latter refused a request to adjust his seat.

"Everything happened very fast," said Sprenger.

"The next thing we noticed they were both on the floor fighting."

Flight, LX196, carrying some 200 passengers to Beijing, headed back to Zurich on Sunday after being in the air around six hours.

During the flight the older man was restrained with cable ties and made to sit in the back row, Sprenger said, adding that the man seemed drunk and yelled for an hour.

A video clip of the older man after the fight was widely circulated on Sina Weibo, with many netizens writing that the incident was humiliating and damaged China's image.

Media officers of Swiss Air told the Global Times that LX197 from Beijing to Zurich was eventually canceled.

A spokesperson of the company told Xinhua that they are still considering taking further action against the two passengers.

Zou Jianjun, a professor at the Civil Aviation Management Institute of China, told the Global Times that people who cause a disturbance on board a flight should be held responsible.

Zou also warned that if a fight between two passengers spread and created widespread chaos the handling of the aircraft could be affected causing devastating consequences.