UPDATED 9.29pm: Seven people are dead after terror attacks in Jakarta, including three suspected perpetrators.

Four people were arrested and three shot dead following the blasts in the capital.
Four people - three civilians and one police officer - were killed around 11am local time today when explosions and shooting broke out on Jl Thamrin, near the offices of the UN.

President Joko Widodo has condemned the act of terror and he's urged citizens not to be cowed.

The president says he's co-ordinated with police on the manhunt for the perpetrators, but he says they all grieve for the victims of the attacks and condemn it.

The president is cutting short his visit to Cirebon, West Java today, and returning to the capital.

A witness has told reporters at the scene the first explosion came from inside a Starbucks cafe.

He says a man then emerged from the chaos with several guns and began shooting randomly, but particularly at police.

Twitter reports describe the explosion as massive - and police appear to be exchanging fire with a shooter. 

Television footage is showing the explosions that went off occurred in the carpark of a Starbucks cafe and the first blast appeared to be larger than the second.

Australian terror expert Greg Barton told Sky News the incident is unfolding outside the Senayan Shopping Mall in an upmarket area home to a number of embassies.

"It's not far north of the Hotel Indonesia roundabout where the premier hotels are located and just south of the UN headquarters located - it's very densely populated with offices and the shopping mall."

There's always lots of pedestrian traffic on the sidewalk.

Jeremy Douglas, a UN regional representative in Jakarta, just flew into Jakarta to hold talks with the Indonesian Government about counter terrorism issues.

He told Rachel Smalley the timing of the explosions is interesting and says Indonesia has a serious problem with foreign fighters that have gone to Syria.

"There are sympathisers of al-Qaeda who are active in the country and they've been threatening to do things like this for some time. You obviously don't know when they're going to do it but it's a serious problem for these countries."

Mr Douglas says the understanding from colleagues who have spoken to police is that it was a suicide bomber but it's unclear. He says they're currently witnessing tactical teams entering the area where the bombing happened and gunfire was being exchanged.

He described to Rachel Smalley what he heard as got out of his car.

"We received a call that a bomb had gone off, then I literally drove into the building at that time...as soon as we got out of the car another one went off then we heard a fourth, fifth and a sixth."

He says there was then prolonged gunfire, which has since stopped.