No injuries were reported but the explosion caused fear among residents of the city, who have had their share of terror in the past, Senior Superintendent Rolen Balquin, Sultan Kudarat police chief, said.
Balquin said the bomb was placed in a sewage drain fronting the bank by unidentified persons.
He said the police were still trying to determine what type of bomb was used to help them identify group behind it. The motive for the bombing remained unclear too, Balquin added.
In August 2011, two people were killed when a car bomb exploded in Tacurong but the authorities said it was not terror-related and was aimed at Maguindanao Governor Esmael Mangudadatu, who was then in a passing convoy.
Previous bomb attacks there, however, were blamed on terrorists linked to the Jemaah Islamiyah.