Police in the Indonesian capital have warned that more bombings are likely in the city following a blast outside a discotheque early Sunday which injured five people.
"We are suspecting that they may plan another series of bombing terror and therefore we call on the people to step up their alertness and report any suspicious incidents to the police," the city's police spokesman said.
Investigations showed the same group was behind the bombing and two other bombs which were found elsewhere and defused, said the spokesman, Senior Commissioner Anton Bachrul Alam.
He said police believed the bombers would strike again because two of their devices were found in time and defused. He declined to give more details.
The bomb which exploded in the parking lot of the Eksotis disco at Mangga Besar in Central Jakarta injured five people, two of them seriously.
Another was found and defused near the 1001 discotheque in West Jakarta. The third was found in the parking lot of the city centre Sarinah department store complex, which also houses night spots.
Alam said the parking attendant outside Eksotis disco was being investigated for suspected negligence. He failed to report a suspicious package which he found under a car and moved it to a noodle stall, where it later exploded. He could face up to five years in jail if convicted.
"From his questioning, he knew that the package was suspicious but he did not report [it to the police]. But he has no links with the perpetrators," Alam said.
Defence Minister Matori Abdul Jalil said the bombing redoubled the government's determination to fight terorrism.
"So if the government of Indonesia is acting firmly in dealing with terrorism, it is not because of pressure from the US government but because that is a need of the Indonesian nation itself," he said.
Jalil told journalists that bombings, irrespective of the mastermind, were an act of terror and not only threatened security but democracy and reforms as well.
Police and the military in Indonesia's second largest city Surabaya, in East Java province, have also stepped up security.
The bomb was the first in the city for months after a spate of blasts between 1999 and 2001 in Jakarta and elsewhere.