The six arrested persons have been identified as Saki Abdul Nachen, Atif Nasir Mullah, Habib Zuber Mullah, Ghulam Sattar, Mohammed Qamil Sheikh and Farhan Abdul Malik Khot.
Those killed in the encounter earlier were Abdul Sultan, Abdul Ali (both Pakistanis) and Mohammed Iqbal (a Kashmiri).
The arrested persons were in touch with their associates in Pakistan and had visited that country a couple of times, Bhujbal said.
Elaborating on the training centres, he said the accused men had visited them on three occasions for imparting training in the use of firearms. The places were being used for the past two years for this purpose, he added.
At least 12 persons had received training at the camps and police are on the lookout for the associates of the six arrested men.
According to Mumbai Police Commissioner R S Sharma, by unearthing the hilltop training venues, the police have dismantled a major 'training module' of the terrorists. They are yet to establish, however, if similar modules exist elsewhere in Maharashtra or India.
"The evidence collected, including some documents, clearly indicates a link between the Ghatkopar blast and the Mulund blast," he said.
"Police have also seized compact discs with speeches linked to the Godhra incident. The speeches by certain religious leaders were found to be provocative and aimed at misleading youths of a minority community," Bhujbal added.