Nepal on Tuesday denounced a deadly explosion in the Thai capital of Bangkok, which has left 20 people dead and more than 100 others injured.

In a message to Thai Prime Minister Prayut Chan-o-Cha, Nepali Prime Minister Sushil Koirala strongly condemned the bomb blast outside a religious shrine in Bangkok and also expressed deep sorrow and grief on the loss of innocent lives.

"The Prime Minister conveyed the deepest condolences and sympathies of the people and the government of Nepal to the Prime Minister of Thailand, and through him to the families and friends of the victims," the prime minister's office said in a statement.

The prime minister has stressed in his message that the perpetrators must be dealt firmly and brought to justice.

The blast took place near a popular Hindu Temple in Bangkok Monday nigh, killing at least 20 people and wounding scores of others.