Video shot by a tourist captured the moment of an explosion outside a Hindu shrine in Bangkok yesterday that killed more than 20 people and wounded at least 120 others.

The footage was filmed by a Chinese tourist walking on an overpass approximately 100 metres away from the blast site.

The man filming could be heard asking, "What's going on?" after the explosion.

Officials have not blamed any group for the bombing at the Erawan shrine, which the government called a bid to destroy the economy. No one has claimed responsibility.

Thai Prime Minister Prayuth Chan-ocha said that authorities were looking for a "suspect" seen on closed-circuit television (CCTV) footage near the site of the bomb blast.

He said the attack, which took place during rush hour in the capital's bustling commercial hub, was unprecedented in Thailand.

Three Chinese were among the dead, China's official Xinhua news agency said. Two Hong Kong residents, two people from Malaysia and one person from the Philippines also died, officials said. Scores of people were wounded, including many from China and Taiwan.

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