Thai police on Wednesday released a sketch of a young, bespectacled man suspected of carrying out a Bangkok shrine bombing that killed 20 people, and announced he was part of a network.

The sketch and comments by the police chief indicating the bomber was not a “lone wolf” assailant were the strongest leads revealed to the public so far over Monday’s attack on the Hindu shrine.

Yet police said they still did not know if he was Thai or foreign and, with no-one yet claiming responsibility, mystery remained over the motive behind the bombing which has no precedent in the kingdom.

“It’s a network,” national police chief General Somyot Poompanmoung told reporters.

“We believe there must be people helping him, Thai people.”

But he revealed no other details.

The attack occurred on Monday evening as worshippers and tourists crowded into the Erawan shrine in the Thai capital’s commercial heart, shredding bodies and incinerating motorcycles.

At least 11 foreigners were killed, with visitors from Britain, China, Hong Kong, Indonesia, Singapore and Malaysia among the victims.

Another 68 people remained in hospital, 12 of whom were in critical conditions.

The police sketch of the suspected bomber showed him with black-rimmed glasses, a full head of dark hair and a light complexion.

Police spokesman Prawut Thavornsiri said his features were gleaned partly from security footage taken of him at the shrine in the minutes before the attack.

That footage, released to the public on Tuesday, shows him wearing a bright yellow T-shirt and dark shorts, walking into the shrine with a backpack.

He casually places the backpack underneath a bench and then slowly walks away clutching a blue plastic bag while looking at what appears to be a smartphone.

Police said he escaped on a motorcycle taxi, a common form of transport in Bangkok, and that the bomb exploded several minutes later.

Prawut, the police spokesman, said other security footage of the suspect was also used to create the sketch, however this was still not enough to determine his nationality.

“(He) might be Thai or foreign,” Prawut said.

Police have offered a one million baht ($28,000) reward for information that leads to the arrest of the main suspect.

Security fears

Police had initially said a second explosion at a Bangkok pier on Tuesday that caused no injuries may also be linked, deepening fears for Bangkok residents of their safety.

But on Wednesday Somyot said the second attack might also be a “copycat” although police were keeping all options open.

Security experts have said they are baffled over who is responsible.

Thailand has experienced a near-decade-long political crisis that has seen endless rounds of street violence.

But it has never seen anything on the scale of Monday’s bomb and foreigners are generally not targets in a country that prides itself on extending a warm welcome to outsiders.

A festering insurgency by Muslim rebels in the Thai south has claimed 6,400 victims—the majority civilians—but it is a highly localised conflict.

With the bomber still on the run and police apparently unsure of who is responsible, ordinary Thais said they feared another attack.

“I’m still scared because you never know where they (the perpetrators) will strike again,” 43-year-old Sommai Gazem told AFP.

Thai junta spokesman Colonel Winthai Suvaree said security had been tightened in tourist areas “especially where there are many Chinese tourists, to regain their trust and confidence”.

Two of the confirmed fatalities were from China, and another two were from Hong Kong.

The Erawan shrine is also close to Bangkok’s Chinatown, and the Chinese government responded to the attack with a call for Thai authorities to ensure the safety of its citizens in Thailand.

Shrine reopens

The shrine, a popular tourist attraction that typifies the kingdom’s unusual blend of Hindu and Buddhist traditions, reopened on Wednesday morning with a ceremony led by chanting monks.

Its surroundings had been largely restored and the pools of congealed blood scrubbed away.

Twisted iron railings were the only immediate sign of the blast point, which police believe was caused by a bomb made up of three kilogrammes of high explosives.

One devotee at the shrine had more reason than most to give thanks.

Tommy Goh, 56, a Thai-Malaysian from Penang, said only a delayed taxi from his hotel spared him from being at the shrine around the time of the blast.

“We were meant to be here around 6:50-7pm but the taxi didn’t arrive from the hotel... so we went somewhere else,” he told AFP.

“Ten minutes later and it could have been so different.”