A Winter Olympics overshadowed by rights concerns and taking place inside a strict Covid-secure bubble will officially begin in Beijing on Friday with an opening ceremony at the "Birds Nest" stadium. The distinctive lattice-shaped arena took center stage at the 2008 Games -- seen as Chinas coming-out party to the world -- and will do so again as Beijing becomes the first city to host both a Summer and Winter Olympics. Fridays opening ceremony starts at 8:00pm (1200 GMT) and will be attended by President Xi Jinping, under whose rule China has become a much more belligerent proposition in global affairs compared to 14 years ago. Xi, who will announce the Games are officially open, will be joined by leaders including his Russian counterpart Vladimir Putin but the United States, Britain, Canada and Australia are among countries staging a diplomatic boycott over Chinas human rights record, particularly the fate of the Muslim Uyghur minority in Xinjiang. Other countries cited the coronavirus pandemic for not sending officials. Their athletes will still compete at the Games, which run until February 20 and are taking place inside a vast "closed loop" designed to thwart the virus. Some spectators will be present at the opening ceremony but it is unclear how many and, like sports events at the Games, tickets were not sold to the general public because of the pandemic. World Health Organization head Tedros Adhanom Ghebreyesus and United Nations Secretary-General Antonio Guterres will be among leaders of global institutions at the ceremony. The show is the mastermind of acclaimed Chinese film director Zhang Yimou, who was behind the 2008 extravaganza. Zhang has promised a "totally innovative" ceremony but conceded that the pandemic and freezing weather will limit its scale compared to the Summer Games, when 15,000 performers took part in a lavish gala featuring opera singers, acrobats and drummers. This time there will be about 3,000 performers and themes will include "environmental protection and low carbon emission", Zhang previously told state media. But Chinas assertion that these will be a "green Games" has been challenged by some experts because they are taking place in one of the driest places in the country and on almost entirely man-made snow. - Not well suited - There are other concerns, including warnings from some Western nations about surveillance of their athletes and what will happen to them if they make anti-China comments or other displays of protest against local authorities. Gus Kenworthy, a British freestyle skier, said he would not be silenced and called China "not well suited" to be hosts. "In my opinion I dont think any country should be allowed to host the Games if they have appalling human rights stances," he told the BBC. On Thursdays eve of the Olympics, about 500 Tibetans marched outside the International Olympic Committee headquarters in Lausanne, Switzerland. They held banners reading "Boycott Beijing Winter Olympics", "Stop human rights violations in Tibet" and "Games of shame". There were also small-scale demonstrations in Los Angeles and San Francisco. Tibet has alternated over the centuries between independence and control by China, which says it "peacefully liberated" the rugged plateau in 1951 and brought infrastructure and education to the previously underdeveloped region. But many exiled Tibetans accuse Chinas ruling Communist Party of religious repression, torture and eroding their culture. - Watching from afar - Concerns about Covid loom large at these Games. The nearly 3,000 athletes and tens of thousands of support staff, volunteers and media have been cut off from Beijings general population. China, where the virus emerged in late 2019, has pursued a no-nonsense zero-Covid policy nationwide and has adopted the same approach to the Games, with everyone cocooned inside the bubble having daily tests and required to wear a mask at all times. They cannot leave the "closed loop" until the Games are over. There have been more than 300 Covid cases in the bubble, among them an unknown number of athletes. Germany said Thursday six members of its team had tested positive on arrival in Beijing, without saying if those concerned were athletes or support staff. Unlike the huge celebration that greeted the 2008 opening ceremony, locals this time will have to enjoy it on television. Zhang Tao, a 43-year-old property developer, said he hoped the Games would have meaning beyond sport. "I really hope the Olympics can sweep away the gloom of Covid," he told AFP.