An approaching motorcycle exploded outside a Roman Catholic church in central Indonesia's Sulawesi Island in a suspected suicide bombing on Sunday, leaving at least 20 people injured, police said.

One death was also confirmed, likely one of the two people on the motorcycle, national police spokesman Argo Yuwono said, adding that among the injured were churchgoers and church security guards.

Police officers stand guard in front of a church in Makassar, South Sulawesi Province, Indonesia, after a suicide bomb attack there on March 28, 2021. (Anadolu Agency/Getty/Kyodo)

A security affairs minister later confirmed that two people "suspected to be the suicide bombers" have died.

The blast occurred during a Palm Sunday Mass at the Most Sacred Heart of Jesus Cathedral in Makassar, the capital of South Sulawesi Province.

"They were trying to enter the church compound when a Mass service just ended but were stopped by the church's security guards at the gate," Argo told a press conference, adding that efforts to identify the perpetrators were underway.

In a statement, President Joko Widodo denounced the explosion as a "terrorist act." He asked the public to go ahead and attend worship services, saying the state will guarantee their safety.

Argo said security will be intensified in churches across the country as the holy week for Christians that ends during the Easter celebrations next Sunday has started.