Island administrator Jon Stanhope told Fairfax Media the roof had been torn off the Rumah Tinggi Bar and Restaurant, one of the island’s oldest and most significant buildings, which is perched on the clifftop of the island overlooking the Indian Ocean.

Speaking as the cyclone was in full force at 8.30am local time (12.30 AEDT), Mr Stanhope said there were no reported injuries and he believed everyone was safe.

The 1700 asylum seekers on the island were likely to be safer than the permanent residents after the Department of Immigration and Serco evacuated them from the areas known as the Construction Camp and Phosphate Hill to Immigration Detention Centre (IDC) buildings, he said.

Mr Stanhope said the IDC was the strongest building on the island and the only one probably built to Australia’s cyclone-proof standards.

He said the time the cyclone had been expected to hit had been continually brought forward as the cyclone gathered speed.

‘‘The impact is quite dramatic. We have gale force winds and the seas, the swell, is right up,’’ said Mr Stanhope.

The Indian Ocean island 2600km north-west of Perth was put on red alert on Saturday morning and residents were told if they had not already evacuated, they must stay in their homes and keep away from doors and windows.

Residents had also been advised to use items such as mattresses and blankets to protect themselves, and stay indoors until an "all clear" signal was given.

The Christmas Island Resort has closed its bar and restaurants and reception areas and staff were sheltering inside their rooms.

The Bureau of Meteorology has warned that the category one cyclone was intensifying and destructive wind gusts of up to 125 kilometres per hour were expected.