Forecasters warned wind speeds could top 130 kilometres (80 miles) an hour when Storm Eowyn hits from the Atlantic, with lashing rain and snow in places.

"It is going to be a damaging, dangerous and destructive weather event," said the chair of Ireland's National Emergency Co-ordination Group, Keith Leonard.

He warned of power outages and told people to stay indoors.

Britain was placed on general alert, with UK-governed Northern Ireland and parts of Scotland under the top-level red warning.

A government spokesman said 4.5 million people in at-risk areas would receive telephone alerts.

Ireland's meteorological office also issued a red alert for the republic.

Jennifer Gilna from Ireland's National Transport Authority said public transport would not operate during the red alerts.

Authorities in Scotland and Northern Ireland said trains and buses would be halted and schools closed.

Britain's environment agency warned of flooding in southern and central England over the coming days.

Scientists say climate change caused by humans burning fossil fuels is making storms more severe, super-charged by warmer oceans.