Two men identified as suspects in the Bangkok bombing have handed themselves in to police, insisting they are tour guides, authorities say.

The pair was seen in security camera footage shortly before Monday's blast at the Erawan Shrine.

The men, in red and white T-shirts, rose from a bench shortly before the main suspect, in yellow, sat down and left behind his backpack.

The attack at the shrine killed 20 people and injured dozens.

Officers are now questioning the pair.

Shrapnel

The police had said that at least 10 people were suspected of involvement in the attack, and that the prime suspect was foreign.

Earlier on Thursday, Col Winthai Suvaree, a spokesman for the ruling military junta, said the preliminary conclusion was that it was "unlikely" the attack was the work of an international terror group.

However, he later told Associated Press that a global terrorism link had not been ruled out, saying: "We still have to investigate in more detail."

The BBC's Jonathan Head in Bangkok says police are also questioning a tuk-tuk taxi driver who drove the main suspect to the shrine, but are making slow progress in identifying the name and nationality of the man in yellow.

He adds that, although the shrine has been cleaned up, a BBC team was still able to find bomb shrapnel embedded in a wall nearby, suggesting the forensic teams have not yet collected all possible evidence from the area.

No-one has yet said they carried out the attack.

National police chief Somyot Pumpanmuang said he believed the attack was planned at least a month in advance.

Prime Minister Prayuth Chan-ocha has called the bombing the "worst ever attack" on Thailand.

Twelve of the 20 dead in Monday's attack were foreigners, including nationals from China, Hong Kong, the UK, Indonesia, Malaysia and Singapore.