Several explosions went off and gunfire broke out in the centre of the Indonesian capital on Thursday and police said they suspected a suicide bomber was responsible for at least one the blasts.
Media said six bombs went off and a Reuters witness saw three dead people and a gunfight going on.
One blast was in a Starbucks cafe and security forces were later seen entering the building.
"The Starbucks cafe windows are blown out. I see three dead people on the road. There has been a lull in the shooting but someone is on the roof of the building and police are aiming their guns at him," said a Reuters photographer.
Indonesia has been on edge in recent weeks over the threat posed by Islamist militants and counter-terrorism police have launched a crackdown on people with suspected links to Islamic State.
According to the official Jakarta police Twitter account one explosion went off in front of a shopping centre called the Sarinah mall, on a main city avenue. Media said a police post outside the mall was blown up.
"I saw a police officer shot right in front of me," one witness told TV One.
Police snipers were deployed, according to media.
A U.N. building near the scene was in lock-down with no one allowed in or out, a witness said. Some other buildings in the area were evacuated.
Indonesia's central bank is located in the same area, and a spokesman for the bank said a policy meeting would go ahead as planned later in the day.
A separate explosion was heard in the western suburb of Palmerah, according to a domestic media tweet, but there were no other details immediately available.
Indonesia has the world's largest Muslim population, the vast majority of whom practise a moderate form of the religion.
The country saw a spate of militant attacks in the 2000s, the deadliest of which was a nightclub bombing on the holiday island of Bali that killed 202 people, most of them tourists.
Police have been largely successful in destroying domestic militant cells since then, but officials have more recently been worrying about a resurgence inspired by groups such as Islamic State and Indonesians who return after fighting with the group.
The last major militant attacks in Jakarta were in July 2009, with bombs at the JW Marriott and Ritz Carlton hotels.
Reuters
