People having houses within the restricted area must convince the authorities that these are authorised, a division bench comprising Chief Justice S.N. Variava and Justice S.K. Mahajan observed.

The bench was hearing a PIL filed by Society for Protection of Heritage and Culture (SPHC) alleging that many illegal structures had come up within the prohibited area near the monument, in violation of Archaeological Survey of India (ASI) Act.

The Act prohibits any type of construction within 100m of a national monument and any alteration in their original architecture.

DDA counsel Sanjay Krishan Kaul said the authority was finding it difficult to implement the court order as there were many ``authorised'' houses within 100m range of the monument. He said the land was acquired by DDA in 1989 and many houses existed there at that time. But the notices were being issued to them, he added.

The court, however, made it clear that persons having legal title to the properties must show their houses were ``authorised'' and the remaining ``must go''. It also said the demolition should be complete and not merely confine to making ``holes'' in the walls, which are, after some time, filled up by the owners.

Counsel for the residents said hundreds of houses will be demolished if the court order was implemented as the area falls within the DDA's marked plan.

To this, the court said the law was clear that ``no structure should come up within the 100 meter area of the monument. Demolition means complete demolition.''

The national monument near Qutab Minar has special significance as the last Mughal king, Bahadurshah Zaffar was confined here by the British rulers before being shifted to Rangoon after the 1857 upsurge. The court directed DDA, ASI and SPHC to file replies by January 17, the next date of hearing.