A BBC reporter at the scene said police have cordoned off the area. He said they were occasionally taking cover behind cars.

There is no indication yet of who might be behind the assault.

Indonesia has been attacked by Islamist militant groups in the past and has been on high alert.

'Gunfire right now'

National police spokesman told AFP people had been warned to stay indoors in case of further explosions.

A UN official, Jeremy Douglas, told the BBC had been about 150m away from one of the blasts near the UN building.

"Then we ran into the building. We heard a third explosion. We got up to our office on the tenth floor and we heard a fourth, a fifth and a sixth.

"There is gunfire going on in the street right now."

A Reuters photographer said one explosion had been at a Starbucks cafe, with its windows blown out.

He said police appeared to be aiming guns at a man on the roof of the building.

This is the first major attack on Jakarta since the 2009 bombing of the Marriot and Ritz hotels.

The BBC's Karishma Vaswani says Jakarta police had been warning of a possible attack for some time, but that this appears to be a very different style of attack from those seen in the city before.