BEIJING, Oct 25 (Bloomberg) - China locked down a county that has seen the most Covid-19 cases in the country’s latest delta outbreak, as an initial flareup in the northwest quickly spirals into a nationwide surge.

Ejin, a county in northwestern China’s Inner Mongolia, has asked its 35,700 residents to stay home from Monday and warned of civil and criminal liabilities should anyone disobey the order, state broadcaster CCTV reported, citing a local government statement. The small county bordering Mongolia is the current outbreak’s hotspot, home to nearly one-third of the more than 150 infections found over the past week in the mainland.

The lockdown came a day after a warning from National Health Commission officials that the outbreak would continue to worsen after spreading to 11 provinces in about a week. China reported 38 Covid infections on Monday, half of which were found in Inner Mongolia.

The capital Beijing -- which has seen a dozen new cases traced back to the northwest -- has all but banned entry by people arriving from anyplace in the country that’s reported having local Covid cases. People who have to visit Beijing from such areas must provide a Covid test conducted no longer than two days earlier, and undergo two weeks of unspecified health monitoring.

Meanwhile, provinces with a handful of cases -- including Beijing; Inner Mongolia, Gansu and Ningxia in the northwest; and Guizhou, in the southwest, have been banned from conducting cross-country travel tours. All train services around China related to tourism have also been halted, as the current outbreak has seen the virus spread quickly among tour groups.

The escalating curbs underscore the challenge even China’s formidable Covid restrictions face in controlling the highly-contagious delta variant. The country is the only nation in the world still seeking to eliminate local transmission of the virus at a time when other so-called Covid-Zero stalwarts -- from Singapore to Australia -- have pivoted to treating it as endemic.

China has managed to quash a slew of flareups since delta first breached its tight border controls in May. One in July and August eventually spread to half of China, forcing authorities to cut transport from hotspots and test local populations multiple times to bring infections back to zero -- only to see new flares emerge.