The Foreign Office has advised British tourists to avoid all but essential travel to several areas in coronavirus-hit northern Italy, including the popular destinations of Venice and Milan.
British nationals are still able to leave Italy without restriction, the FCO added.
Around 16 million people, more than a quarter of the Italian population, have been placed under lockdown as the country’s government tries to halt the spread of Covid-19.
Italy has now registered more cases of coronavirus (7,375) than any country outside China, while its death toll has risen to 366.
Extraordinary measures put in place across Italy, affecting museums, cinemas, shopping centres and restaurants, will be in place until April 3.
In response, the UK’s Foreign and Commonwealth Office (FCO) widened the area covered by its travel advice on Sunday evening to warn against all but essential travel to a number of areas.
The advice covers the Lombardy region, including the cities of Milan, Bergamo and Como, and the provinces of Modena, Parma, Piacenza, Reggio Emilia and Rimini – all in the Emilia Romagna region.
Also included are Pesaro and Urbino in the Marche region; Alessandria, Asti, Novara, Verbano-Cusio-Ossola and Vercelli in the Piemonte region; and Padova, Treviso and Venice in the Veneto region.
Previously the FCO had only advised against all but essential travel to ten small towns in Lombardy and one in Veneto that had been put in isolation by the Italian authorities.
In guidance published on its website, the FCO said British nationals are still able to leave Italy without restriction.
Its advice added: “Residents of other parts of Italy are permitted to leave the isolation areas to return home.
“Otherwise entry into and exit from these areas is forbidden without official permission on the grounds of strict necessity; the authorities have confirmed to us that this will be granted for reasons such as medical need or work requirements.”
Travellers are being told to check their flight details with airlines.
Italian airline Alitalia has suspended all national and international flights from Milan’s Malpensa airport, starting on Monday.
The Department of Health and Social Care is advising people who have travelled to the UK from lockdown areas in northern Italy in the last 14 days to self-isolate, even if they have no symptoms.
Travellers should stay indoors and avoid contact with other people.