A mysterious blast heard near campus of the National Defence University late on Wednesday night created a lot of confusion.

A police team, which reached the site of the blast to seek further information, was told by the naval staff that the explosion was caused by activities during a mock exercise.

"Navy commandos were learning to defuse improvised explosives devices but one of them went off," they said.

However, a police officer said that such an exercise could not be conducted at the odd hour or near such a sensitive installation.