Thai police said on Wednesday they had still not established the nationality or whereabouts of the man they suspect bombed a Bangkokshrine, killing at least 20 people, suggesting the trail had gone cold after he was captured by CCTV at the scene.

Authorities said they were keeping watch for the suspect at the country's borders, but police chief Somyot Pumpanmuang told a news conference that it was not clear how many people were involved in the attack or if they were still in the country.

"I don't suspect one person, I suspect many people," he said. "I am confident that there are Thais involved but I am not saying it is just Thais or that there are foreigners."

On Tuesday, a day after the bombing at the popular Erawan shrine in the heart of Bangkok, grainy closed-circuit television (CCTV) footage was released showing a young man dumping a backpack at the scene and walking away.


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The government says the attack was aimed at wrecking the economy, which depends heavily on tourism.

No one has claimed responsibility for the blast, which according to the latest official toll killed 20 people - more than half of them foreigners from several Asian countries - and wounded more than 120.

Deputy police chief Jaktip Chaijinda said earlier that investigators believed the man on the video resembled a foreigner more than a Thai.

READ: Bangkok bomb suspect part of 'network': Thai police chief

At least two foreigners have been interviewed in connection with the blast, police said.

Jangling nerves in the city on Tuesday, a small explosive was thrown from a bridge towards a river pier, sending a plume of water into the air, but no one was hurt.

A government spokesman initially said there were "patterns" linking the two bombs in that both used the explosive TNT, but police chief Somyot said no direct connection between them had been established.

Police Major General Pornchai Suteerakune, commander of the Institute of Forensic Medicine, said the bodies of almost all those killed at the shrine had wounds inflicted by ball bearings that were packed into the bomb.

The shrine, a blood-spattered scene of charred motorbikes and debris after the blast, was reopened on Wednesday.