Thai authorities on Saturday hunted for culprits behind a wave of bombings targeting popular holiday destinations, as businesses braced for the economic fallout from the attacks on the crucial tourism industry.

The kingdom was on edge after 11 small bombs exploded across five southern provinces Thursday night and Friday morning, killing four locals and wounding more than 30 people -- including foreign tourists.

The bombs, most of them detonated in twin blasts, struck key tourism hubs during a long weekend, including the seaside resort town of Hua Hin and the island of Phuket.

No one has claimed responsibility for the coordinated attack, but police have ruled out international terrorism and said the campaign was an act of ‘local sabotage’.

‘We are confident this was work of a network with a mastermind,’ said deputy police commissioner Ponsapat Pongcharoen, adding that no arrests had been made.

‘It's still unclear what the motive is,’ he said, stressing it was not connected to a simmering insurgency in Thailand's south, as analysts have suggested.

If the Muslim rebels are to blame, it would mark a major expansion of a secessionist campaign that rarely targets foreigners.

It would also be a huge embarrassment to Thailand's coup-installed military government, which has made boosting national security a flagship policy of its regime.

In hardest-hit Hua Hin, a popular beach resort rocked by four bombs in 24 hours, locals said they were fearful the town's mainstay industry would suffer just ahead of peak tourist season.

‘Hua Hin has never had a problem like this,’ Nai Amporn, the owner of a beachside restaurant, told AFP.

‘I am afraid business will become slow -- even this morning, you can see there are fewer people here for breakfast. I think they have all gone home,’ he added.

Hua Hin, about 200 kilometres (125 miles) south of Bangkok, is home to the favourite palace of revered but ailing King Bhumibol Adulyadej, who has spent most of the past few years hospitalised in Bangkok.

-- 'Confidence will return' --

Famed for its idyllic islands and Buddhist temples, Thailand is a tourism powerhouse and was hoping for a record 32 million visitors this year.

The bombings will not affect the tourism industry's target revenue of 2.4 trillion baht ($69 billion) for 2016, Tourism Minister Kobkarn Wattanavrangkul said Saturday.

‘The confidence in tourism will return,’ she told reporters in Bangkok.

‘Thailand solves problems very quickly and always bounces back,’ she added.

Tourism accounts for at least 10 percent of Thailand's economy, which the military government has struggled to invigorate since its 2014 power grab.

‘This will have a significant impact on the tourist season in the south this year and into early 2017,’ said Anthony Davis, a security analyst at IHS Jane's.

He said southern insurgents were the only group capable of carrying out the coordinated attack, dismissing theories that the junta's other political foes were responsible.

‘They have the operational infrastructure and the manpower -- arguably extending the campaign in a striking manner was only a matter of time,’ he said.

Thailand's reputation as a holiday-maker's paradise has in recent years weathered a string of fatal bus and boat accidents, bouts of political unrest and high-profile crimes against foreigners.

After the latest bombings, two Swiss travel companies, Hotelplan Suisse and Kuoni Suisse, said clients with trips to Thailand before August 15 could change or cancel their plans for free, according to Swiss public broadcaster RTS.

The industry has shown previously that it can quickly rebound.

An August 2015 bombing at a Bangkok shrine killed 20 people -- mostly tourists -- and triggered a drop in visitors. But the Kingdom still welcomed a record some 30 million travellers that year.