Police in Uganda said on Sunday they had detained a 28-year-old man entering a church in the capital Kampala with an explosive device he planned to use for an attack there.
Authorities were hunting three other men also believed to have been sent on similar bombing missions elsewhere in Uganda, police said.
The motives were unclear, but the Islamic State (IS)-linked Allied Democratic Forces (ADF) has previously carried out deadly bomb attacks in Uganda.
ADF was originally a Ugandan rebel group but was routed more than two decades ago and fled into the jungles of eastern Democratic Republic of Congo where it has since been based.
The detainee, named as Kintu Ibrahim, was detained as he was about to enter a Pentecostal church, Lubaga Miracle Centre, in the Lubaga suburb of south Kampala.
Police spokesperson Patrick Onyango told journalists security personnel had picked up intelligence about attacks planned on places of worship and that they had tracked Ibrahim.
"We got information that one terrorist had already been sent out to go and carry out a mission, so they followed the terrorist," he said.
Onyango said the suspect had a bag with an improvised explosive device which police detonated safely. During interrogation, Onyango said, he confessed he had three accomplices who had also been sent to carry out similar attacks.
"He's helping us locate those people," Onyango said, adding that the suspect was being held on terrorism related charges.