The Government opened a heritage centre to celebrate the history of its shadowy Internal Security Department (ISD) yesterday but said only a few people would be allowed to glimpse the exhibits on display. Home Affairs Minister Wong Kan Seng said at the opening that balancing the need for secrecy for ISD operatives against the media and public's desire to know about their work remained a tough call. 'Much of the collections displayed in the centre have never been made public; some remain classified,' he said. The ISD, which traces its roots to Singapore's colonial special branch at the start of the 20th century, is in charge of maintaining domestic security in the city-state. Few details about the body are made public, although its staff do brief teachers and other opinion-makers on its clandestine work. The ISD hit the headlines recently with the detention last year of 13 alleged Islamic terrorists who were said to be planning a massive bombing campaign against military and diplomatic targets. The men, who are being held without an open trial, were said to belong to a group called the Jemaah Islamiah, which allegedly has links to Osama bin Laden's al-Qaeda network. Mr Wong said police, immigration officers, civil servants and teachers were welcome to tour the ISD centre and, in time, selected historians and scholars may also be allowed through the door. There was no suggestion, however, that members of the public would be admitted in the near future.