A man threw a small explosive from a bridge in central Bangkok on Tuesday, police said, but it caused no injuries, a day after a bomb at a city shrine killed 22 people, including nine foreigners.

The unidentified man threw the explosive near a busy pier on the city's Chao Phraya river and it landed in a canal, said Colonel Natakit Siriwongtawan, deputy police chief of Klongsan district.

"If it did not fall in the water then it certainly would have caused injuries," he said.