BANGKOK (REUTERS) - A Thai court on Wednesday issued an arrest warrant for the prime suspect in the deadly Bangkok shrine bombing, describing him as an unnamed foreign man shortly after police released a sketch of him.

The warrant, issued by Bangkok's Southern Criminal Court, accuses an "unnamed foreigner of premeditated murder, attempted murder and bomb-making" over the blast that killed 20 people and wounded scores more on Monday.

The sketch of a bespectacled, apparently young man with light stubble and a full head of hair, was published on Wednesday afternoon based on security camera footage taken around the blast site that has been widely shared.

From the sketch it is not immediately clear if he is a foreigner and police have not said how they reached that conclusion.

The warrant is the first major step towards identifying a suspect revealed to the public after he was seen on CCTV calmly leaving a backpack at the Erawan shrine moments before the bomb went off.

Police say the bomber had to have acted with accomplices, with force spokesman Prawut Tavornsiri suggesting there may be "at least two others" involved in the incident and the Thai police chief saying the attack was carried out by a "network."

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.