SYDNEY, March 20 (AFP) -- Australian authorities approved an order forcing people to evacuate their homes Saturday as a tropical cyclone bore down on the Great Barrier Reef, threatening to intensify before making landfall.

The Queensland state government issued a disaster declaration for areas in the path of Tropical Cyclone Ului, which appeared to be gathering force as it closed in on Australia's popular northeast tourist coast, bringing wild storms.

"Some properties may need to be evacuated in the coming hours as Tropical Cyclone Ului approaches and then crosses the north Queensland coast," said state Premier Anna Bligh.

"The declaration gives emergency services agencies the power of mandatory evacuations if required."

Local harbours were crammed with moored yachts and shopkeepers boarded up their storefronts as residents were warned to brace for the worst.

"People should complete preparations quickly and be prepared to shelter in a safe place," the Bureau of Meteorology said. "Boats and outside property should be secured before nightfall."

Ului was 365 kilometres (225 miles) from shore late Saturday, and forecasters said it was expected to hit the coast before dawn on Sunday, bringing heavy rains and damaging winds before weakening inland.

Destructive winds of up to 170 kilometres (100 miles) per hour were expected on the islands and coastal areas closest to the cyclone's centre.

"If it does become a fully-fledged category three cyclone, and there's some chance that it might, that would mean very destructive winds on the coast," senior meteorologist Jim Davidson told state radio.

Hundreds of tourists and residents were earlier this week evacuated from islands on the Great Barrier Reef thought to be in the cyclone's path, and dozens of popular tourist beaches were shut due to dangerous surf conditions.

A 19-year-old was killed when he was knocked unconscious by a ski and disappeared in wild surf whipped up by the cyclone during the Australian Surf Lifesaving Championships Friday.

It is the second time in four years the area has been hit by a tropical cyclone, with a devastating Category Five storm named Larry making landfall near the town of Innisfail on March 20, 2006.

Severe Tropical Cyclone Larry, which gusted at 240 kilometres per hour as its peak, claimed one life and caused almost one billion Australian dollars in damage.