Media playback is unsupported on your device Media caption The BBC's Jonathan Head says Thai police are not linking the attacks to international terrorism

A series of bomb blasts across Thailand has targeted tourist towns, killing four people and injuring dozens.

Four bombs exploded in the resort town of Hua Hin, while several blasts hit the island of Phuket, a top tourist destination, all within a 24-hour period on Thursday and Friday.

No group has said it carried out the attacks, but suspicion is likely to fall on separatist insurgents.

The timing is sensitive, as Friday is a holiday marking the queen's birthday.

The attackers focused on tourist hotspots:

Four blasts over 24 hours in Hua Hin where two people died

where two people died Two blasts in Surat Thani where one person died

where one person died Two blasts in the tourist beach town of Patong on Phuket island

on Phuket island One blast in Trang where one person died

where one person died Blasts in the beach province of Phang Nga

Hua Hin is about 200km (125 miles) from the capital Bangkok while the province of Phuket is in the far south.

Both places, as well as Phang Nga, are known for their scenic beaches. Two bombs went off in front of police stations in Surat Thani within the space of half an hour.

Wendy Herbert, an Australian expatriate who lives in Hua Hin, told the BBC the place was deserted on Friday.

"The main arterial road that runs through, that was near the bomb site, has just been shut down," she said.

"So basically what everyone has been told is stay at home, and I think it's unfortunate because it's Mother's Day and the Queen's birthday in Thailand, so it's a big kind of event day, where everybody would be out and doing things."

Image copyright Reuters Image caption An injured person is rushed away from a bomb blast site in Hua Hin

Image copyright European Photopress Agency Image caption Security was tightened around Hua Hin and at airports in southern Thailand

Who could be behind the attacks?

Police said they had detained some suspects but ruled out international terrorism.

"Initial investigations reveal that two types of bombs were used, which are fire bombs and improvised explosive devices, or IEDs," said Royal Thai Police Col Krisana Patanacharoen.

The bombings, he was quoted as saying by the Associated Press news agency, followed a "similar pattern used in the southern parts of the country".

The BBC's Jonathan Head in Bangkok says that if southern rebels are behind these attacks, it would mark a significant change of tactics. The 12-year conflict in the south has killed more than 6,000 people, but has never targeted tourists.

Security has been tightened in the tourist areas and at airports in southern Thailand.

Foreign embassies have advised tourists to be vigilant. The UK Foreign Office has advised people in tourist areas to "exercise extreme caution, avoid public places and follow the advice of local authorities".

Thailand's southern insurgency

The country's Muslim minority largely originates in the three southernmost provinces of Yala, Pattani and Narathiwat

Insurgents have been fighting since the early 2000s for an independent Islamic state modelled on the old Malay sultanate of Pattani

Security forces, government workers and local Buddhist communities have been targeted in drive-by shootings, bombings and beheadings

The violence has been largely confined to the south

The Thai military and pro-government vigilantes have been accused of a heavy-handed response, including the torture and execution of prisoners

Putting a face to the conflict in the south

Image copyright Reuters Image caption Hua Hin is a town just south of Bangkok popular with tourists

Why have tourist hotspots been targeted?

The attacks have clearly attempted to strike at Thailand's crucial tourism sector.

Image copyright Getty Images Image caption Bloodstains on a pavement in Hua Hin on Friday

"The Thais call it [Hua Hin] a white town because there's so many expatriates who live here," Ms Herbert told the BBC.

"There's a large expat community so the local feeling is, from expats and also from Thais, that this is designed to have maximum impact and damage internationally."

But the choice of Hua Hin as a major target is also symbolic, our correspondent says, being known as a royal city and the king's favoured residence outside Bangkok.

Media playback is unsupported on your device Media caption Footage shows the aftermath of Thursday's bombings in Hua Hin.

Has Thailand seen similar attacks?

Home-made bombs have previously been used by attackers in Thailand at times of political unrest, but since the military took power in a coup in May 2014 such attacks have been extremely rare.

"The bombs are an attempt to create chaos and confusion," PM Prayuth Chan-ocha said to reporters. "We should not make people panic more."

This comes just days before the one-year anniversary of a bomb blast at the Erawan shrine in Bangkok that killed 20 people. The motive has still not been established.

Last week, Thais voted in a referendum which approved a new constitution that will strengthen the military's influence in politics for many years.