More than 1,100 extra security personnel were deployed across Bangkok on Tuesday, the day after a bombing at a tourist site in the Thai capital killed at least 20 people.

Thailand’s military government said it had deployed 1,160 extra security personnel at 88 locations around Bangkok after what Prime Minister Chan-ocha called the “worst ever” attack in the country’s history.

In a televised address, Prayuth pledged to “safeguard [the] life, property and interests” of all inside Thailand.

He blamed the bombing on Monday evening on “individuals or groups that harbor the intention to damage Thailand … by damaging the economy and tourism.”

A possible suspect was seen on local closed-circuit video before the blast, which hit at around 7 p.m. local time.

Security footage showed a suspect carrying a package into the area, Army Chief Udomdej Sitabutr said.

The explosive was said to have been left on a bench beside the popular Erawan Shrine, located at a busy intersection in the centre of Bangkok.

The people killed in the blast included two Malaysians, four Chinese including two from Hong Kong, one from Singapore and five Thais, government spokesman Sansern Kaewkamnerd told reporters.

Eight others were killed but not identified by medical authorities.

No one has claimed responsibility for the attack.

A separate bombing on Tuesday in another part of Bangkok caused no casualties, police said.

Witnesses reported that someone had hurled an explosive device at a busy riverside pier in Bangkok but missed his target and the bomb detonated in the river.

“There was a loud bang and a column of water rose in the air,” said Sean Carter, a music producer based in Bangkok. “We were detained by police and bomb squad for 30 minutes while they searched the area.”

Police spokesman Prawut Thavornsiri told reporters that the device was a pipe bomb, but did not link the incident to Monday’s attack.

Most of central Bangkok was re-opened to the public by Tuesday afternoon although the Erawan shrine was still cordoned off.

Schools and banks opened as usual, and the government insisted that no state of emergency would be declared.

A bomb disposal and a forensics team had earlier checked the area before the remaining debris was removed and the site was hosed down.

Luxury arcades and shops surrounding the bomb area had some of their windows blown out by the blast.

The re-opened area immediately became a site of curiosity for tourists and office workers in the area, many stopping by to take photos.

Some 125 people were injured in the shrine blast.

“There are many people still in hospital whose nationality we can’t determine,” said Dr Phetphong Kamjornjitjakarn, Director of the Erawan Medical Centre, which has been coordinating aid for victims.

“They remain incapacitated and were not carrying any form of identification at the time of the incident.”

The Ministry of Public Health put out an urgent appeal for blood donors as supplies were running low.

“The youngest patient currently in our care is a 5-year-old Chinese national who suffered head injuries,” said Narong Sahametapat, a permanent secretary at the Health Ministry.

“Some patients have been discharged but those suffering from trauma or burns remain in hospital.”

Although such incidents are rare, it is not the first bombing to hit the Thai capital.

Two smaller bombs were detonated in February at a luxury shopping mall in Bangkok near the site of Monday’s bombing, injuring two people.