Hong Kong officials and emergency services held a secret dress rehearsal to prepare for a feared global outbreak of bird flu, the territory's leader said Thursday.

Chief Executive Donald Tsang said extensive contingency plans had been drawn up for an outbreak which he described as "almost inevitable" and "only a matter of time".

A drill to test the reaction of emergency services and government departments had already been held and another one would be staged soon drawing on the lessons of the first, Tsang told reporters.

Medicines are being stockpiled, quarantine areas prepared and intensive care units readied in case the pandemic that health experts fear hits Hong Kong, he said.

Tsang said he was confident Hong Kong was now "as well prepared as any major economy if not slightly better" but warned that outbreaks never struck in quite the way people expected.

He did not give details of when the rehearsal was staged or what it involved during the briefing, held a day after he delivered his maiden policy address as Hong Kong leader.

Hong Kong was the scene of the first bird flu outbreak of modern times to claim human lives when six people died and 18 were infected during an outbreak in 1997.

The former British colony slaughtered all chickens and ducks to prevent the outbreak spreading and has since introduced stringent safeguards that helped it escaped a regional outbreak in 2004.

World Health Organization officials warn that a global outbreak of bird flu with the potential to kill millions of people is likely if the virus that causes it mutates further.

Scientists say the bird flu virus already has the ability to jump the species barrier and infect humans and will become a pandemic once it mutates to pass more easily from human to human.