Chinese President Xi Jinping has urged all-out efforts to search for people who are still unaccounted for and save the injured after an explosion at a fireworks plant in central China's Hunan Province caused heavy casualties on Monday afternoon.

Xi, also general secretary of the Communist Party of China (CPC) Central Committee and chairman of the Central Military Commission, made an instruction ordering strengthened risk screening and hazard control in key sectors, enhanced public safety management, and efforts to safeguard people's lives and property.

The explosion occurred at around 16:40 at the plant in Liuyang, a county-level city under Changsha, capital city of Hunan. As of Tuesday morning, the accident had left 21 people dead and 61 others injured, local authorities said.

Xi demanded proper handling of the aftermath and a prompt investigation into the accident, stressing that those responsible must be held accountable.

Authorities across regions and departments must draw profound lessons from the accident and reinforce responsibility for workplace safety, Xi stressed.

Premier Li Qiang, also a member of the Standing Committee of the Political Bureau of the CPC Central Committee, urged efforts to strengthen workplace safety in key industries and sectors, and resolutely prevent the occurrence of major accidents.

The Ministry of Emergency Management has dispatched a team to Liuyang to guide the rescue and relief work.

Local rescue forces have rushed to the scene to treat the injured and carry out on-site response efforts, which are still underway.

More than 480 rescuers in five teams have been mobilized for the rescue.

As of 08:00 Tuesday, the rescuers had confirmed the casualties following the first round of searching. The injured have been rushed to hospital for treatment and the second round of searching is underway.