The accused, identified as Haroon Rashid Abdul Hamid Naik, is currently in jail in another case.
"Naik. 35, had undergone trainings called 'Daura-E-Aam' and 'Daura-E-Khas' in 2001 at terror camps of Lashkar-e-Taiba in Bahawalpur (Pakistan) after sneaking into Pakistan in late 2000," said a Mumbai police Anti Terrorism Squad (ATS) officer, who did not want to be identified.
"He was then sent to Kandahar in Afghanistan for additional training of 40 days," he added.
According to the officer, Naik allegedly used 'hawala' channels to fund the triple blasts in Mumbai last year. He was also known to Sheikh Omar, the killer of Wall Street Journal reporter Daniel Pearl, and Aftab Ansari, the mastermind of 2002 American Center attack in Kolkata.
Naik was transferred to the custody of ATS Feb 1. He had been earlier nabbed from the Mumbai international airport on charges of possessing fake currency notes Aug 22 last year and was lodged in jail since then.
"Haroon Naik was present when Laden was giving a lecture on jihad in August 2001," the officer said.
He said Naik, a diploma holder in digital technology, had fought alongside Al Qaeda men in Afghanistan.
According to the officer, Naik had come in contact with Aftab Ansari and Sheikh Omar during his training in Pakistan.
The July 13 serial blasts at close intervals shook the country's diamond and gold hubs -- Opera House and Zaveri Bazar -- and the busy commercial area of Dadar, killing at least 27 people and leaving around 125 injured.
The Mumbai ATS had Jan 23 arrested two suspects -- Naki Ahmed Vasi Ahmed Shaikh, 22, and Nadeem Akhtar Ashfaque Shaikh, 23 -- in connection with the bombings.
The ATS is also investigating Naik's role in the financial trail and the conspiracy in this case.