Jakarta: Indonesian police say a suicide bombing that killed three police officers at a busy bus terminal in East Jakarta on Wednesday night was linked to the Islamic State group.
The officers and two suicide bombers died in twin explosions near the Kampung Melayu bus terminal at about 9pm on May 24.
Another 11 people - including six police officers - were wounded in the blasts caused by pressure-cooker bombs.
Asked if the attack was IS related, police spokesman Awi Setiyono said: "Yes, it is related".
The Department of Foreign Affairs issued an updated travel warning on Thursday warning Australians to be vigilant in Indonesia, including in Bali. The overall level of travel advice - exercise a high degree of caution - remained unchanged.
Indonesian President Joko Widodo extended his deep condolences to the victims and their families and called for calm and unity while police were doing their job.
"We have to safeguard calm because within days we Muslims are preparing to enter the month of Ramadan to carry out fasting," he said.
Jakarta-based terrorism analyst Sidney Jones said it was about "90 per cent certain" the perpetrators were from a pro-IS group.
Ms Jones said the perpetrators were likely to be linked to Bahrun Naim - an IS leader in Syria who uses social media to instigate attacks on police - or to the IS-affiliated Jamaah Ansharut Daulah???, which was this year named as a terrorist group by the United States, or another group.
Gruesome images of a decapitated head near the bus terminal and scattered body parts were widely circulated on social media in the wake of the attack.
The explosions came within five minutes of each other at the bus stop and a nearby toilet.
The blasts came after 22 people were killed in a blast at the Manchester Arena in the UK on Monday night after a concert by US singer Ariana Grande and at least 21 people were killed when IS-linked militants swept through the Philippine city of Marawi.
However Ms Jones said it was very unlikely an attack could be mounted in the space of two days in solidarity with two separate incidents in other parts of the world.
"The likelihood is that attacks were in the works in the lead up to Ramadan because we have seen in the past attacks are seen to take on a greater significance," she said.
"Last year, there was an exhortation about a month before Ramadan from the spokesperson for ISIS in Syria to people to wage war at home if they couldn't emigrate to Syria. And that call was heeded by a number of different pro-ISIS groups around the world."
Witness Wilson Mangala told Metro TV he was buying phone credit about 500 metres away from the bus terminal when the attack happened.
"The first explosion I thought was just the normal sound of a bus tire exploding, because we are close to a terminal. About a minute after there was another explosion. Then a man ran by, carrying a victim with a bloodied leg. I asked: 'What is it, pak [Mr]? He said 'bomb, bomb'."
"I didn't believe it at first, there was quite a big crowd, there were scared people who ran and hid in the alleys around here. Some were crying, they were afraid of another explosion.
"I saw body parts, I got so scared, I don't want to look anymore."
Indonesia's largest Islamic civil organisation, Nahdlatul Ulama (NU), said terror groups had a strategy of attacking police in order to break down social order.
"So they try to scare off the police and if police become afraid of them, it is very dangerous," said Supreme Council General Secretary Yahya Cholil Staquf.
"This strategy has been shown in the last few attacks in Tangerang, Jakarta and last night in Kampung Melayu. Their focus was the police."
National Police spokesman Setyo Wasisto said police officers had been providing security for a torch parade to celebrate the Islamic fasting month of Ramadan which starts on Friday.
Evidence found at the crime scene included nails, metal parts and a receipt for a pressure-cooker. A similar bomb was used when a suspected militant linked to IS blew himself up in Bandung in February.
Mr Setyo said police were still investigating whether the blasts were linked to recent attacks around the world.
He said police would provide security ahead of and during Ramadan.
"I call on people not to be afraid," he said. "We must fight terrorism by watching our own neighbourhoods carefully especially if there are unusual things happening."
Mr Setyo praised netizens who posted on social media using the hashtag #KamiTakTakut (we are not afraid).
Prime Minister Malcolm Turnbull tweeted that Australia stands with Indonesia and condemns the "murderous attack" on civilians and police
