The main accused in the twin cinema hall blasts in Delhi, Jaspal Singh, was arrested on Wednesday, police sources said.
The Delhi Crime Branch apprehended Singh, 27, who was on the run since the blasts occurred at Liberty and Satyam theatres on May 22.
One person was killed and over 70 injured in the two blasts.
An activist of Babbar Khalsa outfit was arrested on Tuesday from a village in Jalandhar in connection with the blasts.
Rajesh Kumar alias Sonu was arrested from Malpur village and a 0.30 bore Chinese made pistol along with 70 bullets and different types of explosive timers seized from him.
Jaspal, a Babbar Khalsa militant, was the mastermind behind the twin blasts in New Delhi.
He assembled the bombs in the washrooms of the cinema halls using components smuggled in by him and three of his associates.
While two of them -- Balvinder Singh and Jagannath Yadav -- were arrested last week, the fourth one, Vikas, was still to be traced.
Jaspal and Balwinder, both arrested from Nawashahar district of Punjab, were associated with Babbar Khalsa for some time.
Three other associates of the militants have been arrested with arms and explosives in Nawashahar district in the last few days.