Reacting to the verdict, AIMIM chief and MP Asaduddin Owaisi said "justice not done".
The fourth additional metropolitan sessions-cum-special court for NIA cases had concluded the trial and last week posted the case for judgement on April 16.
The blast at the historic Mecca Masjid here on May 18, 2007 during Friday prayers had also left 58 others injured.
After initial investigation by the local police, the case was transferred to the Central Bureau Of Investigation (CBI), which filed a charge sheet.
Subsequently, the National Investigation Agency (NIA) took over the case from the CBI in 2011.
(Visuals of Swami Aseemanand while being taken to NIA Court. PICS/ANI.)
Ten persons allegedly belonging to right-wing organisations were named as accused in the case.
However, only five of them -- Devendra Gupta, Lokesh Sharma, Swami Aseemanand alias Naba Kumar Sarkar, Bharat Mohanlal Rateshwar alias Bharat Bhai and Rajendra Chowdhary - were arrested and faced trial in the case.
Two other accused -- Sandeep V Dange and Ramchandra Kalsangra -- are absconding while another accused Sunil Joshi died. Investigations were continuing against two other accused.
A total of 226 witnesses were examined during the trial and as many as 411 documents were exhibited.
Swami Aseemanand and Bharat Mohanlal Rateshwar are out on bail while three others are lodged in the central prison here under judicial remand.
In March 2017, a court in Rajasthan had sentenced Gupta and another convict to life in jail in the Ajmer Dargah blast case.
'Rahul Gandhi must apologise'
BJP spokesperson Sambit Patra attacked the Congress for criticising the Court's verdict today. "Why the Congress is showing double standards. Will Rahul Gandhi come out with a candle at midnight to apologise for ‘saffron terror’ remark, Patra asked.