All three blocks that have been cleared belong to Mukesh Ambani's Reliance Industries Ltd and includes India's most prolific gas producing block, the KG-D6, which is situated off the eastern coast.
Of the five blocks that continue to be in "No-Go" areas, three belong to state-owned ONGC and one each to Cairn India and British Gas.
CCI after its first meeting had directed the two ministries to chalk out workable solutions for these eight oil and gas exploration blocks, work on which was stuck due to security reasons.
"All endeavours were made to arrive at a workable solution in respect of granting security clearance to the 'No-Go' blocks, keeping in mind the best practices in other countries as well as options for appropriate ring-fencing and a coordinated mechanism for information sharing between stakeholders," said a joint report by the ministries of defence and petroleum.
RIL's NEC-OSN-97/2 was in the 'No-Go' area as it fell within the 50 km radius of Chandipur missile launch pad of DRDO and about 50% of the block was within the danger zone of IAF's Balasore air-to-air firing range. "The retained area was cleared by Indian Air Force with the condition that DRDO too can clear the area subject to operators taking insurance for possible damages," the report said.
In case of the KG-DWN-98/3 (or the KG-D6 block), sources said that navy had earlier denied clearance for a triangular area on top while agreeing to exploration in the remaining around 70% area.
RIL's KG-OSN-2001/1 has also been cleared with the condition that if exploration and production activities are sought for this block, then 50 km safe distance condition of DRDO will apply.