BANGKOK - Foreigners expressed alarm tinged with a sense of deja vu after a bomb tore through central Bangkok on Monday night in a devastating return of violence to the "Land of Smiles", as Singapore issued a travel advisory for the Thai capital.

At least 19 people were killed by the blast - including one Chinese and one Philippine national - while more than 120 were wounded, many of them tourists who were visiting a popular religious shrine that was the target of the attack.

Whoever laid the device would have known the blast would kill and maim both locals and tourists alike, dealing a further blow to an already struggling economy where tourism has been one of the few bright spots.

Singapore's Embassy in Thailand and Ministry of Foreign Affairs (MFA) advised Singaporeans travelling to or residing in Thailand to avoid the vicinity for the time being.

"They should also monitor the local news and developments closely and heed the instructions of the local Thai authorities. They should also take all necessary precautions for their personal safety, including purchasing comprehensive travel and medical insurance," the statement issued early this morning said.

Since 2006 Bangkok has witnessed repeated rounds of deadly violence, flanked by two coups which have seen the military claim the streets.

But until Monday foreigners had rarely been caught up in the bloodshed.

The Singapore government advisory noted that were three earlier explosions this year reported by Thai authorities: On April 10, a car bomb exploded in the basement car park of Central Festival shopping mall in Koh Samui in the Surat Thani province; On March 7, a grenade exploded outside the Bangkok Criminal Court in the Chatuchak district; and on February 1, two small improvised explosive devices exploded at the Siam station of Bangkok's Skytrain System, in close proximity to the Siam Paragon shopping mall.

The shrine where last night's blast occured sits at the foot of the five-star Grand Hyatt Erawan hotel and is surrounded by a string of large hotels and malls that draw tens of thousands of visitors each day.

By late Monday evening the normally thronging skywalk connecting those shopping centres was virtually abandoned while the streets below filled with police officers and soldiers manning checkpoints.

"It saddens me a lot because the Thais are beautiful people and they're tearing themselves apart for no particular reason at all," said Michael Williams, a 69-year-old Briton who regularly vists the country, speculating that politics was the motive for the attack.

"It won't stop me coming to Thailand, but I'm sure it will damage the Thai economy because people are scared to go anywhere," he told AFP, as he stood outside a hotel close to a police cordon.

"People will definitely think twice about coming to Thailand now," he added.

Howard Fenton, a 50-year-old computer programmer from Australia, said he was dismayed to see violence return once more to Bangkok's streets.

"There's just been so many problems in Thailand over the years," he told AFP. "You sort of hope that it's going to go away but when it comes back again it's pretty shocking. And coming this violently is a real worry."

"I really hope sense will prevail and it doesn't spiral into something really, really shocking," he added.

In a statement released on Monday night in response to media queries, Singapore's MFA condemned the bomb blast in Thailand's capital of Bangkok on Monday night that has killed at least 16 people, including foreign tourists.

It also said it was "saddened by the loss of innocent lives", and conveyed its condolences to the victims' families.

Singapore's Prime Minister Lee Hsien Loong, in a posting on Facebook on Monday night, said his "thoughts are with" those affected by the blasts.

He said staff from the Bangkok Mission have met the Singaporeans injured in the incident, and are rendering assistance to them.

On reports that Singaporeans were injured in the blast, the MFA said it was aiding the affected citizens, and was in contact with the Thai authorities. It is also contacting registered Singaporeans based in Bangkok.

Last night's blasts came just hours after fresh economic data showed Thailand's economy had slowed in the second quarter, hit by weak domestic demand and exports.

Tourism, which accounts for 10 per cent of the country's GDP, was one of the few positive growth areas.

Earlier this month the Tourism Authority of Thailand said arrivals were at 12.4 million in the first five months of this year, a 25 per cent increase on the same period last year when Bangkok was wracked by street protests that eventually led a military coup.

The Erawan is an enormously popular shrine to the Hindu god Brahma but is visited by thousands of Buddhist devotees every day.

It is particularly popular with Chinese visitors, who travel to Thailand in larger numbers than any other nationality.

Thailand had been expecting a surge in Chinese visitors in October for the annual National Day holiday, often dubbed "Golden Week" by China's neighbours because of the huge tourism bonanza it produces.

Soon after the blasts the country's tourism minister Kobkarn Wattanavrangkul visited the nearby Chulalongkorn Hospital where many of the Chinese victims were taken.

"We wanted to make sure there are translators... because a lot of the Chinese they cannot speak English," she told AFP, adding that Chinese speaking volunteers had also turned up at the hospital to help out.

Asked whether the bombs would impact tourism she said: "This is a big concern for us."

- With additional reporting by AFP