The northern Chinese city of Xi'an dramatically tightened Covid travel controls to fight a growing outbreak, with people banned from boarding trains without official permission and hundreds of flights cancelled, AFP reports.

Xi'an reported 52 new coronavirus cases today, bringing the total to 143 since December 9.

From Wednesday, residents are blocked from leaving the city by train without an official letter stating the trip is essential, state broadcaster CCTV reported. It came a day after the city began testing all of its 13 million residents.