BEIJING, Dec 27 (Reuters) - China"s local symptomatic coronavirus cases crept up again, with most new infections reported in the northwestern city of Xian as it entered a fifth day of a lockdown. Xian"s case load - 150 local symptomatic cases on Sunday versus 155 a day earlier - remains tiny compared with many clusters overseas, but it has imposed tough curbs on travel inside and out of town, underpinning Beijing"s drive to contain flare-ups as soon as possible. The latest outbreak has led to 635 local confirmed cases in Xian, a city of 13 million people, during the Dec. 9-26 period, with no Omicron variant infections yet reported. Across mainland China, a total of 162 domestically transmitted COVID-19 infections with confirmed symptoms were reported for Sunday, up from 158 a day earlier, according to official data on Monday. No deaths were reported for Sunday. The new case number marks the highest count of local symptomatic infections since the daily bulletin provided by the National Health Commission started to classify asymptomatic carriers separately from end-March, 2020. Mainland China had 101,277 confirmed cases since the start of the pandemic as of end Dec. 26, including domestically transmitted ones as well as those found among international travellers. The death toll remained at 4,636. In Xian, a two hour flight southwest of Beijing, residents cannot leave the city without approval from employers or local authorities, and households can send only one person to shop for necessities every two days. Other family members may not leave home unless they have essential jobs or urgent matters to attend to, approved by employers or communities. Xian has launched a city-wide disinfection campaign, with staffers spraying pathogen-killing solutions on surfaces of roads and buildings. Residents are advised not to touch plants after the disinfection. It also started a new round of mass testing on Monday, urging residents to stay at home except for having their sample collected. Xianyang city and Weinan city, also in the Shaanxi province where Xian is based, reported one local symptomatic case respectively for Sunday. Local infections were also found in Guangxi region and the provinces of Zhejiang, Guangdong and Sichuan.