A series of car bombs killed 13 people and injured more than 500 in the deadliest attacks to hit the insurgency-torn far south of Thailand in recent years, officials said on Sunday.
In an apparent escalation of their tactics, suspected militants Saturday attacked a hotel in Hat Yai, the largest city in southern Thailand and a popular destination for tourists from neighbouring Malaysia and Singapore.
A car bomb in the basement triggered a fire which spread to a shopping mall within the Lee Gardens Plaza Hotel and killed three people, including a Malaysian tourist, according to the police.
Songkhla provincial governor Grisada Boorach said 416 people were injured, mostly suffering from smoke inhalation, and 140 were still in hospital Sunday.
Until now Hat Yai and Songkhla province have been relatively untouched by the shadowy insurgency that has claimed thousands of lives in the neighbouring Muslim-dominated provinces of Yala, Pattani and Narathiwat since 2004.
"There is no hint why they did this at this time," Hat Yai police chief Colonel Khomgrit Srisong told AFP by telephone. "We're questioning witnesses and the injured for more information."
The hotel bombing came about an hour after two car bombs minutes apart hit the town of Yala around midday as people were out shopping.
Those blasts killed 10 people and wounded 117 others, 29 of whom were still in hospital, said Colonel Pramote Promin, spokesman for the southern army region.
National police chief General Priewpan Damapong said the hotel bombing was linked to the Yala attack. "It was a car bomb and it's related to the incident in Yala and I believe that it was the work of the same group," he said in televised remarks.
Colonel Pramote also said the attacks seemed similar. "The incident in Yala and Hat Yai are similar in term of the type of operation and the period of time," he said on TNN24 television.
"In the south there are not many insurgent groups who operate like this." A complex insurgency, without clearly stated aims, has plagued Thailand's far south near the border with Malaysia since 2004, claiming thousands of lives, both Buddhist and Muslim, with near-daily bomb or gun attacks.
However, they are rarely as deadly as Saturday's explosions. A string of shootings in Yala province left 10 people dead in August 2007, while nine people were killed by a bomb in a village in January last year, also in Yala.
The insurgents are not thought to be part of a global jihad movement but are instead rebelling against a long history of perceived discrimination against ethnic-Malay Muslims by successive Thai governments.
Struggling to quell the unrest, authorities have imposed emergency rule in the region, which rights campaigners say effectively gives the army legal immunity.
The military has admitted that troops shot dead four Muslim villagers on their way to a funeral due to a "misunderstanding" in late January after apparently fearing they were under attack from militants.
One of the region's deadliest incidents occurred on October 25, 2004, when seven people were shot dead as security forces broke up a protest in the town of Tak Bai, and 78 more suffocated or were crushed to death in trucks while being transported to a detention centre.
Rights groups have said the failure of Thai authorities to hold security forces to account over the deaths has fuelled further violence and alienation in the southern region.