Members of the bomb squad inspect the site of bomb blast detonated by suspected separatist militants at the clock tower intersection in Pattani town.

Bangkok - A grenade blast killed four people and injured about 40 during a festival at a temple in north-eastern Thailand on Monday, police said.

The grenade went off about 1.00am after police attempted to seize it from Winai Jeknam, 32, at the Nadu Pagoda in Mahasarakham province, 500 kilometres north-east of Bangkok.

Two policemen were killed by the blast, which also ripped off Winai's right arm, Police Colonel Kritchai Saluamsri told the Khao Sot newspaper.

The blast also killed two bystanders and injured about 40 others, he said.

Kritchai said the suspect had an argument earlier with someone attending the annual festival, and had returned with the M67

grenade. The pin had already been removed when police attempted to take it from him.Authors: Somchai Kwankijswet and Peter Janssen - Sapa-dpa