At least 16 people were killed and dozens injured when a bomb exploded Monday outside a religious shrine in a bustling hub of the Thai capital popular with tourists, authorities said.

The blast occurred about 6:30 pm (1130 GMT) when the streetside shrine was packed with worshippers and tourists -- with the Thai police chief confirming at least 10 Thais, one Chinese and one Filipino citizen were among the dead.

"It was a bomb, I think it was inside a motorcycle... it was very big, look at the bodies," one visibly shocked rescue volunteer, who did not want to be named, told AFP outside the Erawan Shrine.

Bangkok has endured years of deadly political violence, with a military junta now ruling the nation, and a decades-long Muslim insurgency in the far south that has claimed thousands of lives.

Police spokesman Prawut Thavornsiri told AFP the blast was likely politically motivated and designed to bring "chaos", adding 16 people had been confirmed killed.

However no-one claimed responsibility for Monday's attack, and it was unclear immediately who may have been responsible.

A spokesman for the government later said it was too early to speculate on who was behind the attack.

Islamic militants have carried out many attacks in other parts of Southeast Asia, including on Indonesia's holiday island of Bali in 2002 that killed 202 people, but they have not made Thailand a prime target.

Glass was strewn across the street after the explosion inside the gates to the shrine, which is in the central Chidlom district popular with tourists, an AFP reporter witnessed.

Charred and shattered motorcycles littered the scene, along with hunks of concrete, with pools of blood on the pavement and two bodies crumpled on the steps of the shrine.

The city's medical emergency centre said more than 80 people were wounded by the blast, which rattled windows several kilometres from the site.

There were chaotic scenes at Chulakongkorn Hospital, one of a number of nearby medical facilities that received victims as nurses ferried the injured on gurneys.

One man who was conscious had visibly burned hair and a number of cuts that were bandaged, an AFP reporter on the scene said.

"Some (of the victims) are Chinese," Minister for Tourism Kobkarn Wattanavrangkul told AFP as she visited the hospital.

A Chinese and a Filipino were among those confirmed dead, Thai police sai, while Singapore's prime minister said some of the city-state's nationals were also wounded.

With rumours abounding in a city that is no stranger to major acts of violence, officials denied reports of more devices in an area, which is home to several high end hotels and major shopping malls.

While there was no immediate claim of responsibility for the attack, the initial comments by Thai police cast immediate suspicion on the kingdom's rival political factions.

Thailand has been seared by a near-decade of political violence that has left the country deeply divided and seen repeated rounds of deadly street protests and bombings -- but none on Monday's scale.

Many observers had predicted a fresh round of violence after the military seized power in a coup in May last year, toppling a civilian government led by Yingluck Shinawatra.

Thailand's defence minister said the bombers had targeted "foreigners" to try to damage the tourist industry, which is a rare bright spot in an otherwise gloomy economy.

 

"It was a TNT bomb... the people who did it targeted foreigners and to damage tourism and the economy," said Prawit Wongsuwong, a former general who is believed to have been one of the key coup-makers.

Singaporean and Taiwanese authorities said their citizens were among those injured.

Self-exiled former premier Thaksin Shinawatra, who is Yingluck's brother and who was toppled by a 2006 coup, sits at the heart of the political divide.

Parties led by him or his sister or supporters have won every election since 2001 thanks to the votes of the rural north and northeast. But he is loathed by the Bangkok-based royalist elite.

Thailand is also fighting a festering insurgency in its Muslim-majority southernmost provinces bordering Malaysia. More than 6,400 people -- mostly civilians -- have been killed there.

In the so-called "Deep South", bombs are a near-daily reality alongside shootings and ambushes of security forces.

Civilians are overwhelmingly the target. But the conflict, which sees local rebels calling for greater autonomy from the Thai state, has stayed highly localised.

There has never been a confirmed attack by the insurgents outside the southern region despite the years of war. 

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

It is located on a traffic-choked intersection in Bangkok's commercial hub and surrounded by three major shopping malls.