Li Keqiang, the Chinese Premier, has called for an immediate investigation into a scandal over faulty vaccines that he said had crossed a moral line, and urged severe punishment for the companies and people implicated.

The scandal erupted a week ago, after major vaccine maker Changsheng Biotechnology Co was found to have violated standards in making rabies vaccine for humans. There did not appear to be reports, however, of people harmed by the vaccine or having contracted rabies after receiving it.

The case has sparked anger on social media and dealt a blow to China's drug regulator, which has been struggling to clean up the world's second-biggest drug industry and promote domestically made vaccines.

In a statement posted on the government's website late on Sunday, Li said the public deserved a clear explanation.

"We will resolutely crack down on illegal and criminal acts that endanger the safety of peoples' lives, resolutely punish lawbreakers according to the law, and resolutely and severely criticise dereliction of duty in supervision," he was quoted as saying.