There was another attack on a different police station in the city last night, about 12 hours after 14 people were killed in three separate attacks on Surabaya churches.
Members of one family were responsible for the church attacks, including a mother and two young girls wearing suicide belts.
The first attack, at the Santa Maria Roman Catholic Church, killed four people, including one or more bombers, a police spokesman said.
Minutes after the first, there was a second explosion at the Christian Church of Diponegoro that killed two people.
Another two people died in a third attack at the city's Pantekosta Church, the police spokesman said.
Police say four officers and six civilians have been injured in another suicide attack in Indonesia's second-largest city of Surabaya.
Pantekosta Church was one of the initial targets in the first wave of explosions on Sunday. Photo: AFP
Today's explosion occurred about 1.50pm NZT outside the local police headquarters.
CCTV footage that captured the moment the bomb was detonated shows two motorbikes pull up alongside a car and four officers manning the checkpoint.
At the moment of the explosion, two civilians appear to be walking into the checkpoint just metres from the motorbikes.
Three of the officers at the checkpoint are standing right by the motorbikes when the detonation happens.
There was another attack on a different police station in the city last night, about 12 hours after 14 people - including six suicide bombers - were killed in three separate attacks on Surabaya churches.
Members of one family were responsible for the church attacks, including a mother and two young girls wearing suicide belts.
The first attack, at the Santa Maria Roman Catholic Church, killed four people, including one or more bombers, a police spokesman said.
Minutes after the first, there was a second explosion at the Christian Church of Diponegoro that killed two people.
Another two people died in a third attack at the city's Pantekosta Church, the police spokesman said.
Police suspected the new attacks were also by extremists linked to the Jemaah Ansurat Daulah group.
"Clearly it's a suicide bombing," East Java police spokesman Frans Barung Mangera told a media briefing.
"We can't be open [about] all details yet because we are still identifying victims at the scene and the crime scene is being handled."
The full extent of casualties was unclear, he said.
Indonesian President Joko Widodo said the series of suicide attacks in Surabaya was the "act of cowards" and pledged to push through a new anti-terrorism bill to combat networks of Islamist militants in the country.
"This is the act of cowards, undignified and barbaric," Mr Widodo said on Metro TV.
He would issue a regulation in lieu of a law next month to force through a new anti-terrorism bill if Parliament failed to pass it, he said.
Indonesia's chief security minister said police backed by the military would step up security across the country.
"The president has commanded that police, helped by TNI [the armed forces], to exert all power to secure the nation," coordinating minister for political, legal and security affairs Wiranto said.
-ABC/Reuters