Police say a member of rebel group KNU clashed with ‘rival gangster’ in Tak province, but group denies involvement.

Authorities in Thailand have arrested two men following a blast at a festival near the border with Myanmar that killed three people and wounded dozens.

Thai police said an improvised explosive device had been thrown into a crowd on a dance floor at a crowded festival in Umphang district in Thailand’s northern Tak province just before midnight on Friday.

The explosion killed two people instantly, with another dying later in hospital and 48 left injured among the approximately 8,000-9,000 attending the event.

Police said a Thai youth and a man belonging to the Karen National Union (KNU), a rebel group fighting for autonomy in neighbouring Myanmar’s Karen state, had been arrested.

Tak police chief Major-General Samrit Ekamol said the Myanmar suspect had thrown the bomb after encountering a “rival gangster” he had previously fought with.

But a senior KNU official contacted by the AFP news agency, who declined to be named as he was not authorised to speak to media, denied any involvement and said the group did not have any members in the area.

Thanathip Sawangsang, a spokesperson for the Ministry of Defence, told The Associated Press that local police had reported a fight between rival groups of men before the explosion and that there was no wider security threat.

He said the forensic evidence showed the explosive device was a homemade bomb.

Tak province has a heavy military presence in its border areas, including in Umphang.

Prime Minister Paetongtarn Shinawatra expressed her condolences to the victims’ families and urged security agencies to carry out an investigation.