"We have porous sea borders. Unless we secure this area we are going to be defenceless as during the Mumbai attacks," Singh said at a programme by defence PSU Garden Reach Shipbuilders and Engineers Limited (GRSE) here.
Talking to reporters he said that the government is concerned about the security issue.
"Internal security is about internal vigilance and so we are in the process of being vigilant," he said.
When asked about the situation along the Jammu and Kashmir border, he said it is fully secured as it was fenced.
"Unfortunately if there is an intention on the contrary that people on one side want to get on to the other side then they devise means - whether its through underground tunnels or by crossing the fence. We have to be vigilant," Singh said.
On illegal immigration from Bangladesh side, the central minister said "We are well aware of the situation. We are a bit apprehensive. We are doing whatever we can under the circumstances."