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PATTANI, Thailand (Reuters) - Muslim militants fighting for a separate state in the south of predominantly Buddhist Thailand were suspected of carrying out a car-bomb attack on Tuesday outside a supermarket in the city of Pattani that wounded 60 people, authorities said.

A decades-old separatist insurgency in the largely ethnic Malay Muslim provinces of Yala, Pattani and Narathiwat has killed more than 6,500 people since 2004, according to independent monitoring group Deep South Watch.

Most of the wounded were discharged after receiving treatment but 21 with more serious injuries were hospitalized, Arun Prasertsuk, deputy director of Pattani Hospital told a local television channel.

The blast destroyed the front of a Big-C supermarket, scattering debris over a wide area and sending up a column of black smoke.

Muslim insurgents were suspected of carrying out the attack, deputy police chief Rewat Srichantub said. He said the bomber was believed to have fled before the explosion. It was the first car bomb in Pattani since August.

Defense ministry spokesman Kongcheep Tantrawanit said the government condemned the bomb attack and considered it a grave violation of human rights.

Attacks in Thailand’s deep south, near the border with Muslim-majority Malaysia, have intensified this year. Six army rangers were killed in an attack last month.

The government recently rejected a conditional offer for peace talks from one of the main insurgent groups, the Barisan Revolusi Nasional, which demanded international mediation or observation.