Rescue efforts are continuing after a bomb blast hit a shrine in the commercial centre of the Thai capital, killing at least 20 people and injuring at least 78.

The explosion went off around 7pm local time on Monday at the Erawan Hindu Shrine on a busy city intersection. 

Notes from the field - Maher Sattar

Not too long after the blast, the police started to cordon off the area. As I was walking away I saw one of the officers picking up what looked like little cotton pads that were soaked in blood - probably a leftover from someone trying to treat one of the wounded in the aftermath of the blast.

At the spot of the blast there was a motorcycle on the street, blown into at least two pieces. Officials in the area were looking around for more bombs - I kept hearing that more bombs had been found - there were a lot of rumours going around.

Soon, all of the press and passersby gathering in the area had to move further and further away - they were expanding the search area for more bombs - the area was not risk-free.

Al Jazeera's Wayne Hay, reporting from near the scene, said officials said it appeared a pipe bomb had been placed in the grounds of the shrine, discounting earlier suggestions that several other explosive devices had been discovered in the area.

Defence Minister Prawit Wongsuwan said: "It was a TNT bomb... the people who did it targeted foreigners and to damage tourism and the economy."

Those killed included at least two Chinese nationals, the Chinese embassy said.

The Thai government called for calm in the wake of the attack and vowed to hunt down those responsible, our correspondent said.

There has been no claim of responsibility.

Prime Minister Prayuth Chan-ocha called an emergency meeting with high-level government officials and military officers in charge of national security in the wake of the attack.

While the area has been cordoned off and security in the capital has been lifted, a state of emergency has not been imposed.

Al Jazeera's Veronica Pedrosa, who was earlier at the scene, said when the blast occurred, "people were running for their lives".

"Bodies, twisted metal and debris were scattered across the street at a place popular with locals and tourists," she said.

Eric Seldin, of Thaicom Production Services, was 100 metres away when the bomb exploded.

"I was inside the Hyatt hotel having dinner when we heard an extremely loud explosion near the Ratchaprasong intersection," he told Al Jazeera. "The windows were shattered and everyone at the hotel was startled.

"Security tried to shut down the hotel and attempted to keep everyone inside but I was able to go out and walk just about 50 metres close to the intersection.

"I noticed seven to eight covered bodies. There was damage to the ground of the shrine.

"On the street itself there were several casualties. There is a large security presence. Police are moving people back because they are worried about the second explosion.

"The area is extremely close to the National Police Headquarters and the police hospital," Seldin said.

Different tactics

Thai forces are fighting a low-level Muslim insurgency in the predominantly Buddhist country's south, but those rebels have rarely launched attacks outside their ethnic Malay heartland.

Our correspondent Hay said officials have said the bombing did not "match their tactics".

The country has also been riven for a decade by intense and sometimes violent rivalry between political factions in Bangkok and elsewhere. 

Al Jazeera spoke to people at the scene of the explosion.

Somrudee Prayunwong [Maher Sattar / Al Jazeera]

Somrudee Prayunwong, Resident

We don't want to think about what will happen next - the death toll has been rising so quickly, we're afraid to think about how bad it could be.

We live near here. We didn't think it would be a bomb, we thought something else had happened.

Prayoong Supharot [Maher Sattar / Al Jazeera]

Prayoong Supharot, Motorcycle Taxi Driver

At 6pm I heard something that sounded like thunder. But it turned out to be something much worse - something that never should have happened. So a bunch of us motorcycle taxi drivers who were by the intersection went into a hotel nearby to hide.

When we heard there was an explosion we became frightened, and each of us went to find out own hiding spaces.

After the explosion there was silence. Then we all went out to see what had happened. We saw body parts scattered all over - corpses of people... we couldn't tell what nationalities they were.

At first we saw that five people had died - then it turned out to be more than we had expected. It felt like something that shouldn't have happened - right in the heart of the city. We don't know why it happened, but of course everyone is frightened now.

Malee Roongrueng [Maher Sattar / Al Jazeera]

Malee Roongrueng, Street Vendor

This doesn't affect me that much, I'm pretty used to all this - I've seen the red shirt protests, I've seen bombs in telephone booths.

I was nearby when I heard the blast - I thought it was thunder. Then I walked back and someone told me it was a bomb - I was shocked!  

Source: Al Jazeera and agencies