Insurgents on Wednesday targeted the heart of Saudi Arabia's security services, destroying a key building and killing at least six personnel.

"This is a quantum leap by Jihadi groups, as they have gone from aiming at American targets to Saudi security forces," said Muhammad al-Massari, representing the London-based Committe for the Defence of Legitimate Rights, campaigning for reform in the Saudi kingdom.

Another dissident, Saad al-Faqih, said the incident did not happen out of the blue, but follows "months and years of heavy government campaigning against those groups fighting for reform".

The target, al-Faqih told Aljazeera.net, was not an isolated building, but "the nerve centre of security in the country". 

Faqih heads the Movement for Islamic Reform in Arabia, also based in London. 

'Not working at all'

Wednesday's incident came amid an intense crackdown on insurgents that has seen numerous arrests and the seizure of three explosives-laden vehicles.

The latest explosion, said Faqih, was almost "a conclusion that the regime's campaign was not working at all".

"The Saudi regime is in big trouble and only God knows where it will end"

Muhammad Al-Massari, CDLR

Both Faqih and al-Massari concurred the government's approach to reform was creating fertile ground for violence.

By arresting even peaceful reformists, Faqih said, Saudi authorities were proving that "there was no room for peaceful action in the country". 

Saudi Arabia has arrested many dissidents in recent weeks after they spoke out against the ruling monarchy.

"The Saudi regime is in big trouble and only God knows where it will end," said al-Massari.