A pipeline explosion at a power station in China killed at least 21 people and injured five more on Thursday, the official Xinhua news service reported.

The blast, which Xinhua said happened in a high-pressure steam pipeline, came a day before the first anniversary of giant explosions that killed at least 165 people in the northern port city of Tianjin.

The latest incident occurred at a coal-fired power plant in Dangyang, in the central province of Hubei, and rescue efforts were underway, reports said.

A photograph purportedly from the scene showed a bare concrete shell and metal scaffolding standing by a smokestack.

The local government said it was investigating the cause.

Three people were seriously injured and were being treated in hospital, reports said.

Newspapers said the company operating the coal-fired plant was registered for power generation and sales of slag ash and petroleum products.

Industrial accidents are common in China, where safety standards are often lax.

Earlier this summer more than 130 people were taken to hospital after chemicals leaked from a plant in eastern China.

In April a chemical fire burned for 16 hours in the coastal province of Jiangsu after an explosion at a facility storing chemicals and fuel, requiring 400 firefighters to quell the flames.

The massive blasts in Tianjin, which caused over $1 billion in damages and killed at least 165, sparked widespread anger over a perceived lack of transparency by officials about the accident's causes and environmental impact.

A government inquiry into the Tianjin accident released in February recommended 123 people be punished.