
Thai police have admitted they knew bomb attacks were imminent but didn't warn anybody as explosives hidden in plant pots across the country killed four people and injured dozens more.

Foreign visitors fled in terror and are now being warned to be on alert, as the first two blasts hit the seaside resort of Hua Hin overnight, killing one Thai woman and one other and wounding 21 people.

The twin bomb attack targeted a busy street filled with bars and restaurants. The town was also hit by small explosions on Friday morning.

Hours later two small bombs were detonated in the beach town Patong, Phuket, another area popular with foreign tourists. One man was said to have been 'lightly wounded' in the attack. His nationality is not yet known.

A woman is carried by two Thai officials after being injured in the twin bomb blasts in Hua Hin overnight. Witnesses described how revellers fled in terror from one of the main roads in the town, popular with visitors and residents

A tourist receives treatment on the street after being injured in an explosion in the Thai seaside resort of Hua Hin on Thursday night. The country has been hit by a wave of co-ordinated bomb attacks targeting areas popular with visitors

A woman is treated on a street by two soldiers in the seaside resort of Hua Hin after being injured in twin bomb attacks overnight

A group of terrified young tourists speak to a Thai official after the blasts in Hua Hin, which wounded 10 foreign nationals

Rescue workers rush to help one of those injured in the blasts in Hua Hin. A woman died in the overnight attacks

At least four locations in southern Thailand have been hit in the past 24 hours - Trang, Hua Hin, Surat Thani and Phuket

Thai police and media have also reported similar strikes in the southern regions which killed one person in Surat Thani and and another in Trang, with both used as stop-off points for many visitors travelling on to the country's islands.

There were also reports of blasts or fires in Phang Nga and Krabie and two men are being detained and questioned over the attacks.

Today, national police chief Chakthp Chaijinda told reporters in Bangkok his officers had intelligence an attack was to happen but said they had no precise information on location or timing.

He said: 'We just didn't know which day something would happen,'

Now western governments have been issuing advice to their citizens in Thailand telling them to be cautious.

The British embassy in Thailand has updated travel advice urging tourists to exercise 'extreme caution' and avoid public places.

Australians have been warned to exercise a 'heightened caution' in the country and follow the advice of local authorities.

While the United States also urged travellers to use caution and avoid the affected areas.

A young woman is strapped to a stretcher after being injured in the bomb attack in Hua Hin to be taken to hospital for treatment

Two injured people receive first aid from passers-by after two bombs exploded in the Thai seaside resort of Hua Hin

A woman is seen here clutching to a man as the pair lay on the ground waiting for help following the Hua Hin attacks

A victim is seen on the ground after a bomb exploded in Hua Hin - one of four locations hit in the past 24 hours

Explosive Ordnance Disposal (EOD) official checks at the scene of a bomb blast in Hua Hin. It is believed the bombs had been left in plant pots

There has also been two explosions in the southern Thai town of Surat Thani following the first two bomb blasts in Hua Hin

A man who was blown off his feet and is left lying on the pavement is assisted by a bystander after the blasts in Hua Hin

Thai medics rush an injured victims into an ambulance to hospital after two bomb exploded in Hua Hin close to the city's clock tower

Thai officials have said they believe the attacks were carried out locally and are not terror related. There is some suggestion they were launched by the opponents of the ruling junta, which recently bolstered its military power.

ARE THE ATTACKS ARE PART OF GROWING UNREST IN THAILAND? Police believe the attacks were part of a growing unrest with the country's government - rather than terror-related. Thailand's junta chief on Friday called a series of bombings that killed four people in 24 hours an attempt to trigger unrest in a country blighted by a decade-long political crisis. 'The bombs are an attempt to create chaos and confusion,' junta chief Prayut Chan-O-Cha told reporters in Bangkok. 'Why have the bombs occurred as our country is heading towards stability, a better economy and tourism - and who did it? You have to find out,' he said. The violence took place on the 84th birthday of Thailand's Queen Sirikit. Thailand's 88 year-old King Bhumibol Adulayadej, the world's longest reigning monarch, and his wife Sirikit are in hospital in Bangkok but have resided in Hua Hin at the Klai Kangwon Palace royal palace. Advertisement

And junta chief and Thai leader Prayat Chan-O-Cha branded the attacks as an 'attempt to create chaos and confusion.'

Nine foreigners were among the 21 people injured in the Hua Hin blasts were foreign nationals, according to local officials. Dutch, Austrian, German and Italian nationals are believed to have been affected.

A statement from the German foreign ministry confirmed that at least three German nationals had been injured in the blast in Hua Hin and that the embassy was offering them assistance.

Tourist Shane Brett described the scenes of panic after the first devices were detonated in Hua Hin.

He told the Australian Broadcasting Corporation: 'I was at a bar in the main bar district in Hua Hin right outside the Hilton Hotel and at first I heard kind of a bang and everyone kind of panicked.'

Mr Brett said revellers fled to safety, adding there were 'a good few people injured and the whole area just panicking ... the whole area was just shut down with police cars, ambulances'.

While Henrik Buuz, 62, of Denmark sipped beer in a Hua Hin hotel lobby Friday.

He said that while he might not have taken security seriously in the past, he no longer felt safe in the sunny beach town where streets were remarkably quiet for the beginning of a three-day holiday.

'No, no, no, no. Now we don't think it's funny anymore,' said Buuz.

In Surat Thani, provincial governor Wongsiri Promchana said the bomb, hidden in a flower bed, exploded in front of the marine police offices, killing a municipal worker and injuring another man.

'I think it's related to the blasts in Hua Hin,' Wongsiri told AFP, referring to the overnight attack in the town that lies further north.

According to local media one person died in an attack on the Centre Point shopping mall in Trang while six more were injured.

General Sithichai Srisopacharoenrath said the devices were hidden inside plants on a street filled with restaurants, bars and food sellers that is popular with tourists and residents.

He said a Samsung mobile phone had been recovered that they believed was used to detonate at least one the bombs.

Thai tourism minister KobarnWattanavrangkul meets Italian tourist Lorenzo Minuti who was injured during one of the bomb attacks in Hua Hin

Italian tourist Andrea Tazzioli, 51, who was injured during the bomb attack in Salakam road, smiles for a photograph on his bed at Sanpaulo hospital

On Friday, debris and ball bearings could be seen strewn across the road as police investigated the scene. The blast damaged a pair of phone booths and shattered the window of a nearby Starbucks.

Speaking at a press conference on Friday, Army General Danai Kritmethavee said authorities believed the attacks were coordinated and that they are investigating 'all possible leads'.

While national deputy police spokesman Piyapan Pingmuang told reporters: 'This is not a terrorist attack. It is just local sabotage that is restricted to limited areas and provinces'.

A member of the Thai Explosive Ordnance Disposal team wearing a bomb suit defuses a suspicious device found in Hua Hin

Security services use a detector to scour the area close to where the twin blasts occurred in Hua Hin last night and this morning

An investigation official collects evidence from the crime scene after the explosion which ripped through bars and shops

A Thai police officer secures an area next to a portrait of King Bhumibol Adulyadej and Queen Sirikit in Hua Hin

Debris and ball bearings could be seen strewn across the road as police investigated the scene. The blast damaged a pair of phone booths and shattered the window of a nearby Starbucks

Analysts said Muslim insurgent groups in the south could be behind the attack, but warned that coordinated bombings targeting tourists would mark an unprecedented escalation in a simmering conflict largely contained in the border region.

Some reports suggest that the timing of the strikes, which took place on the 84th birthday of Thailand's Queen Sirikit, gives weight to the theory they were carried out by those opposed to the junta.

The junta has repeatedly said that defending the monarchy is a top priority and the army and its allies are keen to ensure a smooth succession for ailing King Bhumibol Adulyadej, 88, who has a palace in Hua Hin.

Surat Thani police told local media NationTV, that there are 'similarities' between bombs in Surat Thani (pictured) and Trang

It is thought there are eight or nine foreign tourists among the injured, pictured, who have been taken to a local hospital where they were treated for their wounds

Thais voted less than a week ago in a referendum to adopt a military-backed constitution, the first test of Prime Minister Prayuth Chan-ocha at the ballot box since he seized power in a coup in May 2014.

The three provinces near the border with Muslim-majority Malaysia soundly rejected the referendum on the new military-backed constitution which passed convincingly in most of the rest of the country in Sunday's vote.

TIMELINE OF TERROR IN THAILAND Thursday, Trang 3pm - A bomb detonated by a mobile phone kills one person and injures six at a market in the southern city. Hua Hin 10.15 and 11pm - Two explosions close to each other hit a street popular with tourists in the beach city southwest of Bangkok. The second blast kills one woman and injures 21. Friday, Phuket 7.45am - An explosion at Loma beach at the southern beach city injures one person. Surat Thani - 8am - An explosion near a police station during an event celebrating the Thai queen's birthday kills one person and injures three in the southern city. Surat Thani 8.30am - No one is hurt in an explosion at another police station. Phuket 8.45 am - No one is hurt in an explosion near a police traffic control booth. Hua Hin 9am - Two bombs in plant pots under the Hua Hin clock tower detonate within minutes of each other. One person is killed and three are injured. Phang Nga 9am - Two bombs detonate in front of a market in the southern province. No one is hurt but two cars are damaged. Advertisement

It is thought more than 6,500 people, including Buddhist monks, teachers, troops and separatist insurgents have been killed since 2004 in the long-running conflict, although tourist destinations have rarely been affected.

The latest bombings came almost a year after an attack by two ethnic Uighur Muslims from China on a Hindu shrine thronged with tourists in central Bangkok killed 20 people and wounded more than 120.

Police also ruled out the possibility international militants may have been responsible for that attack, and said the perpetrators were members of a network that trafficked Uighurs and launched the attack in anger at a crackdown.

Analysts, diplomats and even some officials suspected the attack was linked to sympathisers of China's Uighur minority angered by the Thai junta's deportation of more than 100 Uighurs to China the previous month.

King Bhumibol and the queen are both in hospital in Bangkok and have not stayed recently at their palace in Hua Hin. Check points have been established and security beefed up around Hua Hin and the palace there.

The king has received treatment for an infection over the past month in hospital, the Royal Household Bureau said on August 1. Concern about the health of the king and nervousness over the succession have played into the country's political tensions.

The resort of Hua Hin is popular with both foreigners and locals, and hosts international jazz, car and kite festivals every year.

It is also famous for its fishing opportunities while its shallow and warm waters provide good conditions for kite boarding and surfing.

Small bombings are common in the kingdom during periods of heightened political tension but there have been few such incidents in the past year and it is rare for tourists to be targeted.

Phuket in particular is frequented by millions of European, Chinese and Thai tourists each year who come to swim in the warm, azure sea, party at the open air night clubs and explore tropical rainforests. The other towns hit are less prominent international destinations but still popular among Thais and many foreigners.

Tourism suffered a temporary hit after a bomb blast ripped through a Bangkok shrine nearly a year ago, killing 20 people, mostly visitors from other Asian countries.

'This ruins business. Hotels, restaurants, tours, we were already suffering, but this, it's going to ruin our lives,' said Hua Hin Adventure Tours guide Natsupa Dechapanya.

Natsupa raced Thursday from hotel to hotel visiting clients and warning them not to go outside, especially where people gather. She was also fielding cancellation calls, although she was staying away from her office, opposite a clock tower where Friday's bombs went off.

'I'm scared, it's bad,' she said. 'This is the first time this has happened in Hua Hin. We think of this as a safe town, but now everyone is fearful. We feel like we're not safe.'

She said because the explosions happened hours apart, many - including herself - are worried about whether the attacks are over. And she said without any arrests, tension on city streets is palpable.

'Usually this is a friendly town, but today no one wants to look up. People don't want to look each other in the eyes,' she said.

The bombings killed one Thai woman, who was believed to be a street vendor at the resort, pictured, which is popular with western tourists