BEIJING, Jan 6 (Reuters) - More cities in central China"s Henan province imposed COVID restrictions as infections there rose sharply, while authorities in the northwestern city of Xian apologised on Thursday to a woman whose miscarriage during lockdown stirred public outrage. Henan reported 64 domestically transmitted infections with confirmed symptoms for Wednesday, up from just four a day earlier, official data showed on Thursday. While those numbers are small by global standards, and no cases of the highly transmissible Omicron variant have been reported so far in Henan, several cities there imposed new limits on travel and other activities in response. China"s policy of stamping out clusters quickly has taken on extra urgency in the run-up to the Winter Olympics, to be staged in Beijing and neighbouring Hebei province starting Feb. 4, and with the Lunar New Year holiday travel season beginning later this month. In Gushi, a Henan province county of 1 million residents, officials stopped people from leaving and discouraged visitors, although it reported only one symptomatic case and one asymptomatic carrier for Wednesday. Nearly all of the more than 4 million residents of Xuchang in Henan province, meanwhile, were to be tested for COVID-19 on Thursday and Friday and movement of people was to be minimised, while the 1 million residents of Yuzhou city, under Xuchang"s juridiction, were in lockdown. Mainland China has only announced a handful of Omicron cases from international travellers and at least one locally transmitted infection, but it has intensified efforts to reduce the risk of the variant being brought from overseas. Travellers from the United States, where Omicron is spreading rapidly, must complete a nucleic acid test seven days before departure and report their body temperature daily for one week, on top of existing requirements, according to notices published on Tuesday by China"s U.S. embassy and consulates. In Xian, a city of 13 million that has been under lockdown for 15 days, limiting normal access to medical services and leading to complaints about food supplies, a health official apologised during a news briefing on Thursday to a woman who had lost her unborn baby after waiting outside a local hospital for two hours. The incident had provoked anger on Chinese social media. Liu Shunzhi, the director of the city"s health commission, also apologised for "unsmooth access to medical treatment" for people with special needs. State media reported on Thursday that Liu and another Xian health official were warned by authorities over their performance during the outbreak, while the hospital"s general manager was suspended and some other staffers removed from their roles. International passenger flights into Xian"s airport were halted from Wednesday, the official Xinhua news agency reported on Thursday. Domestic passenger flights had already been suspended.