A deadly weapon that's easy to make
Insurgents in Iraq use them to blow up police stations, Colombian rebels use them to kill lawmakers, and Israel used them to assassinate militia leaders in Beirut.
Car bombs are the weapon of choice in the Middle East but uncommon in Hong Kong, until yesterday's fatal blast.
Experts say it is not hard to make such a bomb, with instructions easily available on the internet and explosives not difficult to obtain.
'All the information is readily available in the public domain. It is not that difficult to find the information. Materials-wise, it would not be that difficult. Everything can be purchased in Asia,' said Philip Lomax, an associate managing director at security firm Kroll.
He was supported by International Risk president Steve Vickers. 'A simple car bomb is not difficult,' he said. It could be triggered by a timer, pressure pad on the seat, or through remote control by a mobile phone or similar device.
A bomber would need access to explosives, 'which is not that difficult if you are in the construction industry' or had been in the military, he said.
The small crater left by yesterday's bombing indicated a high explosive was used, Mr Vickers said.
These included plastic explosives such as C4 and Semtex, which were more powerful and more stable than dynamite.
An internet search yesterday found several sites advertising bomb recipes.