Bomb blasts ripped through the JW Marriott and Ritz-Carlton hotels in Jakarta's business district on Friday, killing nine people and wounding dozens in attacks that could dent investor confidence in Indonesia.
A car bomb also blew up along a toll road in North Jakarta, police said without giving further details. Indonesia's Metro TV said two people had been killed. An unexploded bomb was also later found at the Marriott, police said.
The apparently coordinated bombings are the first in several years and follow a period in which the government had made progress in tackling security threats from militant Islamic groups, bringing a sense of political stability to Southeast Asia's biggest economy.
Some analysts have already cast suspicion on remnants of the Jemaah Islamiah group, blamed for previous attacks including a car bombing outside the Marriott in 2003 as well as bombings on the resort island of Bali the previous year that killed 202 people.
Here are some questions and answers on security in Indonesia:
IS THIS UNEXPECTED?
Yes. Indonesia had made enormous progress in containing the threat from militant group JI which security officials and analysts said was behind several fatal bomb attacks on Western targets including hotels and bars in Jakarta and the resort island of Bali.
The Indonesian authorities, with help and training from their Australian and U.S. counterparts, have increased security and surveillance in recent years.
Indonesia's security forces have detained hundreds of militants and killed several during shoot-outs, carrying out numerous sweeps, even in recent weeks.
HOW COULD THESE NEW ATTACKS HAPPEN, HAS SECURITY BEEN RELAXED?
There are no outward signs security measures have been relaxed in Jakarta. The security presence was stepped up around the time of the presidential elections on July 8, which passed peacefully.
All the major hotels in Jakarta have security checks outside to reduce the risk of car bombs, although checks in many are not particularly thorough, with a security guard just poking his head in the window to look at who is inside the car.
Although the Marriott and Ritz were known for exceptionally tight security barriers and checks, including for those entering the hotel on foot, from the damage at the scene of the blasts it appears the bombs exploded inside the hotels, and were either brought in by suicide bombers or planted inside and set off by timers.
IS JEMAAH ISLAMIAH BEHIND THIS?
Several analysts are already saying these attacks have some of the hallmarks of JI, which in the past has chosen high-profile targets such as Western hotels and bars frequented by foreigners.
JI has used car bombs in the past, but barricades and layout changes as well as other measures at the best-protected luxury and Western hotels in Jakarta and Bali have made it harder for that kind of attack.
DOES THIS MEAN JI HAS RECOVERED AND IS A THREAT AGAIN?
If it is indeed JI, this suggests they still have bomb-making capability and operatives, despite having lost many of their trained and skilled members.
IF IT ISN'T JI, WHO ELSE COULD IT BE?
In 1998, when former autocratic President Suharto was desperately trying to retain power, some elements within the military were accused of stirring up social unrest and riots in an attempt to cause widespread panic and destabilise Indonesia.
There have been other instances in Indonesia's history when military elements were suspected of being behind unrest in order to have an excuse to clamp down on civilians.
The country has also sporadically seen violence including bombings attributed to various separatist groups, political organisations, and criminal gangs.
WHAT LONG-TERM IMPACT COULD THIS HAVE ON INDONESIA?
It's certainly a blow for Indonesia's security forces and the country's risk profile, particularly coming so close on the heels of peaceful elections in the world's third-largest democracy.
Indonesia had begun to stand out among its Southeast Asian peers as a stable democracy that was making real progress in tackling corruption in order to attract foreign investment.
These attacks could make some investors think twice before committing to any new, long-term, strategic investments in areas such as natural resources or infrastructure.
That said, however, the market reaction has been relatively muted.