Police officials said a loud noise was heard and thick grey smoke was seen immediately after in the area, where dozens of supporters of the two presidential candidates - President Joko Widodo and Prabowo Subianto - had gathered on Sunday.

There were no immediate reports of casualties or injuries.

"It was fireworks. We are still working on it," national police spokesman Dedi Prasetyo told Reuters.

Unverified videos circulating on social media showed people running away from thick smoke in a parking lot and several police officers cordoning off an area near the hotel.

Indonesia is set to go to the polls on April 17.

Australian Associated Press