BEIJING, Dec 23 (Reuters) - Rising COVID-19 infections in China's city of Xian have spurred a lockdown of its 13 million residents, with stretches of highway eerily bare on Thursday, as many people queued in the cold to get their noses swabbed at testing sites. The daily count of domestically transmitted infections with confirmed symptoms in the northwestern city, famed for its terracotta warriors buried with China's first emperor, has increased for six straight days since Dec. 17.