Two people on a motorbike have carried out a suicide bombing at a police HQ in Surabaya, a day after a wave of deadly blasts in the Indonesian city.
Police officers were injured in the explosion, which occurred at 08:50 local time (01:50 GMT), but the extent of casualties was not immediately clear.
At least 13 people were killed in bomb attacks on three churches on Sunday.
The Islamic State group has said it was behind those attacks.
Indonesian President Joko Widodo described the string of attacks as "cowardly, undignified and inhumane".
"There will be no compromise in taking action on the ground to stop terrorism."
It was not yet clear whether the attacks were connected to deadly blasts on Sunday.
East Java police spokesman Frans Barung Mangera said full details could not be given yet "because we are still identifying victims at the scene and the crime scene is being handled".
Police have said the family who carried them out were among hundreds of Indonesians who had returned from Syria, where IS has been fighting government forces. No details were given about the family's alleged involvement in that conflict.
The father has been identified as Dita Oepriarto. Police say he was the head of local branch of Jemaah Ansharut Daulah (JAD), an Indonesian IS-inspired network.
In the first attack, the sons - aged 16 and 18 - rode motorcycles into Santa Maria Catholic Church at around 07:30 local time (00:30 GMT) and detonated explosives they were carrying.
The father then reportedly dropped off his wife, Puji Kuswati, and their two daughters at Diponegoro Indonesian Christian Church, where they blew themselves up. The girls - aged nine and 12 - had bombs strapped to them, as did their mother.
Oepriarto then drove off, launching his own bomb-laden car into the grounds of Surabaya Centre Pentecostal Church, police said.
Thirteen people were killed and more than 40 injured, making it the deadliest attack in Indonesia in more than a decade.
The South East Asian country has long struggled with Islamist militancy. Its worst ever terror attack was in Bali in 2002, when 202 people - mostly foreigners - were killed in an attack on a tourist nightlife district.
That attack was carried out by the Jemaah Islamiah (JI) militant network.