One woman was killed and scores more were injured when two bombs exploded in a market in Thailand’s deep south, one of the worst attacks against civilians in five years of separatist violence.

Five of the victims were seriously injured with shrapnel wounds to the head or torso, after the morning attack in the province of Narathiwat that left at least 70 hurt. Just before lunchtime a car bomb packed with some 30kg of explosives detonated as a group of village leaders were emerging from a meeting.

A few minutes later, as helpers rushed to the scene of the attack, a smaller bomb attached to a motorcycle exploded in front of a nearby teashop. Police said they were both set off by mobile phones.

“The insurgents aimed to kill,” Thailand’s prime minister, Somchai Wongsawat, said. “Most of the wounded were civilian officials who were leaving the meeting and heading for their cars. The bombs show that the wrongdoers want to attack places where there are many people. [They] want to make trouble and keep the unrest going.”

More than 3,400 people have been killed in a brutal undeclared war between the Thai security forces and a ghostly, cruel and mysterious Islamic insurgency which began five years ago next January. Its victims have included monks, teachers and soldiers from the Buddhist north of the country, as well as Muslim villagers, and many real or alleged insurgents killed by the security forces.

On average, somebody is murdered most days in southern Thailand. This past week alone, two men in their 40s were shot dead in separate attacks in Narathiwat and neighbouring Pattani province. A monitoring group called Deep South Watch reported 18 similar killings in the first two half of October – and this was the lowest murder rate in four years.

Despite the ongoing bloodshed, the security forces seem to have made little progress in stamping out the insurgency, or even identifying its leaders and goals. It is assumed that the aim of the attacks is to drive out Buddhist migrants from the North, and establish the three southernmost provinces of Narathiwat, Yala and Pattani as an independent sultanate – which they were until their incorporation into Siam a century ago.

But there have been no manifestos or demands, and there are no active insurgent websites or spokesmen. Nor is there any sign that the movement has been infiltrated by international terrorist organisations such as Jemaah Islamiyah, the al-Qaida affiliate which carried out the Bali bombing in 2002.

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