Thai authorities have said they are hunting a foreigner and at least two other men suspected of carrying out the devastating bombing of a Bangkok shrine that killed at least 20 people.

National police spokesman Prawut Thavornsiri said on Wednesday that the prime suspect had been overheard speaking a foreign language other than English.

Prawut also said the suspect looked like he may have been from the Middle East, South Asia, or Central Asia, using a Thai term to describe light-skinned individuals from those regions.

Police also released a sketch of the suspect shown on security footage walking into the shrine and placing a backpack believed to contain the bomb, which detonated a few minutes later.

Authorities said the attacker did not carry out Monday's bombing alone, and two other suspects have been identified in CCTV footage of the blast site.

Officials various times said that they did not rule out any group, including elements opposed to the military government, though they said it did not match the tactics of Muslim fighters in the south or "red shirt" supporters of the previous administration.

Foreigners dead

An image released by the Royal Thai Police on August 19 [Reuters]
The attack left at least 11 foreigners dead, with Chinese, Singaporeans, Indonesians and a family from Malaysia among the victims.

More than 100 other people were wounded by the blast that struck at one of the city's busiest intersections.

On Tuesday, the police released grainy closed-circuit television (CCTV) footage of a young man wearing a yellow t-shirt.

Police said the sketch could help locate the yellow-shirted man seen in the CCTV footage. A 1 million baht ($28,000) reward has been offered to anyone who can give police information leading to his arrest.

Shrine reopened

On Wednesday, Buddhist monks led prayers for the reopening of the shrine located in busy Ratchaprasong commercial district.

A small explosion on Tuesday by a bridge at the city's Chao Praya River has been tied to Monday's bomb.

Colonel Kamthorn Ouicharoen, of the Thai bomb squad police, confirmed the bridge bomb was the same type as the one detonated at the Erawan shrine.

Thailand has experienced a near-decade long political crisis that has seen endless rounds of street violence, but never anything on the scale of Monday's attack.

Al Jazeera's Scott Heidler, reporting from Bangkok, said the bombings came just as tourism is rebounding in Thailand.  

"The arrival numbers of the all-important Chinese market doubled for the first half of this year compared to the same period last year," he said.

"The UN tourism organisation said these were direct attacks on Thais and the country’s economy that’s strongly connected to tourism."

About 10,000 additional security forces have been deployed in Bangkok after the bombing, reassuring some tourists.

"At first I was shocked to hear about the blast. After assessing the situation, I think Bangkok might be safer after the bomb," one Chinese tourist told Al Jazeera.

Source: Al Jazeera and agencies