The arrestee identified himself as Golam Rasul, 30, of Shibganj upazila in Chanpainawabganj.

Security guards in the corridor connecting the first floors of the Bar building and the Court building first barred Rasul from entering the building at about noon as he could not explain why he wanted to get inside.

After some time, he made another attempt to go inside the building through the second floor. But a security guard who was watching him carefully caught Rasul and took him to the intelligence officials deployed on the court premises.

The intelligence men found a diary in his pocket and a money receipt of Chanpainawabganj unit of Jamaat. The notebook contains a couple of sentences like 'we will have to work plan wise'; 'Police have arrested Waliullah.' It also has some jottings of expenses, said intelligence sources.

Under interrogation, Rasul claimed himself to be the superintendent of Raniganj AB Dakhil Madrasa.

He said he came to Dhaka for a work he had to do at the Madrasa Board and went to the High Court building just to sightsee.

Rasul said he checked in Hotel Kader on Alauddin Road in Old Dhaka on December 11.

Later when he was handed over to Ramna police, they arrested him under section 54 of Criminal Procedure Code. He will be produced before Chief Metropolitan Magistrate's Court, Dhaka today.

Rasul told Ramna police that he is an activist of Jamaat-e-Islami.