Wreckage of motorcycles are seen as security forces and emergency workers gather at the scene of a blast in central Bangkok August 17, 2015. REUTERS/Athit Perawongmetha

A China Central Television reporter quoted police in Bangkok as saying that TNT was used in the bomb, and that a bomb disposal unit had dismantled two suspected explosive devices.

"The perpetrators intended to destroy the economy and tourism because the incident occurred in the heart of the tourism district," Defense Minister Prawit Wongsuwan said.

The Erawan shrine, on a busy corner in the Thai capital near top hotels, shopping centres, offices and a hospital, is a major attraction, especially for visitors from East Asia, including China. Many ordinary Thais also worship there.

"I had just paid tribute to the Buddha. I was washing my hands, and suddenly I heard a huge explosion, and when I turned, four people were all lying on the ground," Gu Xinlun, a Chinese tourist who arrived in Bangkok on Monday, told China Daily.

He said the blast killed one of his friends.

"It was like a meat market," said Marko Cunningham, a New Zealand paramedic working with a Bangkok ambulance service, who said the blast had left a two-metre-wide (6-foot-) crater.

"There were bodies everywhere. Some were shredded. There were legs where heads were supposed to be. It was horrific," Cunningham said, adding that people several hundred metres away had been injured.