Beijing is stepping up its oversight of exports of coronavirus test kits after several European countries complained about the accuracy of some Chinese-made tests. Chinese exporters of coronavirus tests must now obtain a registration certificate from the National Medical Products Administration (NMPA) in order to be cleared by China’s customs, the NMPA said in a statement late on Tuesday. Beijing had been encouraging Chinese firms to export test kits and other supplies to help battle the coronavirus pandemic, leading to a surge of companies offering kits to countries desperate to get a handle on the fast-moving and highly contagious disease.