LISBON: Britain and Ireland braced Sunday for a lashing from Ophelia, the largest hurricane ever recorded so far east in the Atlantic Ocean, after it dumped heavy rains on Portugal's Azores islands.

As the storm passed near the Azores archipelago on Saturday it was classed Category 3, which means it packed winds of at least 178 kilometres (110 miles) per hour.

Though the storm will weaken as it churns toward Ireland and Britain, it still packs enough power to damage buildings and provoke "dangerous" sea conditions as well as potential flooding, authorities said.

Ophelia is the fifteenth named storm of the 2017 Atlantic season, which is expected to last until the end of November.

Three major hurricanes -- Harvey, Irma and Maria -- caused catastrophic damage in the Caribbean and the US Gulf Coast.

According to meterologists, Ophelia is the most powerful hurricane recorded so far east in the Atlantic and the first since 1939 to travel so far north.

But by the time it reaches Ireland on Monday it is expected to weaken to a "post tropical storm" with severe winds and stormy conditions, according to the US National Hurricane Center.

Seven of the nine islands in the Azores were on high alert for the storm's passage, but it did not cause major damage, authorities told reporters.

Still, firefighters responded to calls of flooding and a downed tree on the island of Sao Miguel. Several flights between the islands or mainland Portugal were cancelled, affecting about 800 passengers.

Five counties in the west of Ireland will be placed on red alert for "severe" weather conditions from Monday morning to early Tuesday, the Irish Meteorological Service said.

People in those counties are advised "to take action to protect themselves" and their property.

As a result bus services have been cancelled on Monday for schoolchildren in the five western counties because officials fear the students "could therefore be exposed to severe elements", said operator Bus Eireann.

"Schools will make their own decisions on whether to open or remain closed," it said. "We are aware this decision may cause inconvenience, but safety of schoolchildren is our number one priority."

Mean wind speeds in excess of 80 kilometres per hour and gusts of over 130 kph are expected, the weather service said.

Parts of Britain, meanwhile, have been placed on yellow alert for Monday and Tuesday, the lowest warning level triggered by "serious" weather conditions.—AFP