A Thai military court issued an arrest warrant for a second suspect on Tuesday over a series of bombings that killed four people last week.

"The court has approved the arrest warrant for one suspect for the explosions. We can't say who that individual is," Chaiyapol Chatchaidet, commander of the Counter Crime Planning Division, told Reuters

On Sunday, the police had arrested one suspect for arson.

Defence Minister Prawit Wongsuwan on Monday said that southern insurgents might have been hired to carry out the dead bomb attacks. But he also said the bombings were not an extension of a separatist war in the three southern-most Muslim-dominated provinces of the country.

No group has claimed responsibility for the attacks yet but the officials have clearly ruled out any link to foreign militants.

The bombings took place just days after Thailand approved its new military junta-backed constitution.