Around 10,000 paramilitary troops and police are manning a heavy security blanket around normally sleepy Islamabad. Roadblocks have been erected at all entry points to the city where passers-by were being frisked and vehicles checked for bombs.

A so-called "red zone" covering a radius of around two kilometers (just over one mile) has been established around the two main hotels where heads of state and senior delegates are staying, and the Convention Centre where opening and closing ceremonies will be held.

"It is one of the most stringent security operations in the history of the country," said a senior security official.

Anti-aircraft guns and troops have been positioned in the Margalla hills overlooking the city while popular hiking and jogging tracks have been declared out of bounds.

All schools, colleges and religious seminaries will remain closed for a week.

Security for the Saarc summit became the top concern after two attempts to assassinate President Pervez Musharraf in the adjoining city of Rawalpindi.