China further tightened its anti-pandemic measures in Beijing and across the country on Friday as scattered outbreaks continued ahead of the opening of the Winter Olympics in a little over two weeks.

The actions appear to reflect nervousness about a possible surge in cases ahead of the Beijing Games.

Beijing has ordered children at international schools to be tested starting next week and is barring air passengers who transited via a third point. Citizens are being told only to travel if absolutely necessary, with no guarantee they will be permitted to return if found to have visited a city or region where an outbreak occurred.

The city of Tianjin, about an hour from the capital, has ordered a third round of mass testing starting Saturday morning to be completed within 24 hours.

A port and manufacturing center with 14 million people, Tianjin is one of a half dozen cities where the government is imposing lockdowns and other restrictions as part of a policy to track down every virus case.

It’s proximity to Beijing is particularly worrying and authorities have cut off all travel links between it and the Olympic host city following the discovery of 126 cases in recent days, all apparently of the highly contagious omicron variant.