Indonesian President Joko Widodo on Thursday said multiple blasts that hit Jakarta, killing at least four people, were "acts of terror".

"Our nation and our people should not be afraid, we will not be defeated by these acts of terror, I hope the public stay calm," he said on TV station MetroTV.

"We all are grieving for the fallen victims of this incident, but we also condemn the act that has disturbed the security and peace and spread terror among our people."