British Prime Minster Boris Johnson has ordered the closure of most retail stores and banned gatherings for three weeks in a stepped-up response to slow the new coronavirus.

The measures Johnson announced in an address to the nation on Monday night are more closely aligned with sweeping actions taken in France, Spain and Italy but mark a departure from the British government's until-now more relaxed approach to the worldwide COVID-19 pandemic.

Britain has already closed schools, bars and restaurants and urged people to stay home. But while many followed the instructions, some did not.

The approach has led to confusion, and caused alarm by public officials worried about the ever escalating numbers of cases.

There were growing calls for the government to impose tighter restrictions with more rigorous enforcement.

Johnson said that he was giving “the British people a very simple instruction - you must stay at home.’’

He offered a list of limited purposes for which leaving home would be allowed, including essential shopping, medical appointments and one form of exercise a day.