Thailand bomb attack
Thai police officers stand at the site of an explosion on 12 August, 2016 in Hua Hin Dario Pignatelli/ Getty Images

Thai police have stepped up security at Bangkok's airport and major landmarks following a tip-off about a possible terror attack. Thailand's national security head said an armed group was planning a car bomb attack in a province near Bangkok.

"The deputy prime minister instructed security agencies closely track and monitor anything unusual including things used to prepare bombs and cars," Reuters quoted Thawip Netniyom, chief of Thailand's National Security Council, as saying.

Without giving details on which group the police suspect could be planning the attack, Netniyom said: "Why target Bangkok? They probably want to make an impact."

Thailand's southern territory has come under a series of bomb attacks in recent times. Attacks across the country on 11 and 12 August killed four Thai nationals and injured dozens, including two Britons. Within two weeks, another bomb blast took place in the country's Pattani district killing one person and injuring two.

Netniyom added there were no specific targets and that he could not confirm if the current planned car bombs were linked to the August attacks.

"I have ordered all police under my supervision in the area around Bangkok to monitor news, investigate and gather intelligence on groups who could come in and cause trouble," said police Lieutenant General Charnthep Sesawet, acting chief of Provincial Police Region 1, which oversees areas around Bangkok.

While Thai authorities have maintained they have found no terrorist motive behind the attacks, they have linked some of the blasts to Muslim separatists operating in the country's far south.

Critics have said the denial could be an attempt to avoid deterring tourists, especially westerners, as tourism is the lifeline of the country, accounting for 10% of its of gross domestic product (GDP).

The UK Foreign Office had issued a travel advisory to its nationals asking them to be cautious while travelling to Thailand following the August attacks.

"You should exercise caution, particularly in public places ... Further incidents are possible in these and other areas of Thailand," the Foreign Office had said.