LONDON — Ireland’s prime minister says coronavirus restrictions will be tightened in the country amid concerns that the new variant of the virus identified in southeast England has spread across the Irish Sea.

In an address to the nation, Prime Minister Micheal Martin said the government was acting “quickly and aggressively” in response to rising infection rates and that it was proceeding on the assumption that the new variant, which is said to be more virulent than existing strains, was already in Ireland.

He said that in the last week, the country had seen “extraordinary growth in the spread of the virus.” Figures, he said, suggest the virus is growing by around 10% a day.

Among the new restrictions to be imposed over the coming days and to last until Jan. 12, Martin said restaurants and pubs selling food will have to close at 3 p.m. on Dec. 24. So-called “wet pubs” — those that don’t sell food — are already closed.

Shops and schools can stay open, he added.