LONDON — British authorities are likely to tighten restrictions on more areas of the country this week, amid mixed signs about whether recent measures have stemmed a steep rise in coronavirus infections.

Government scientific advisers say there are some signs the increase has begun to level off since a three-tier virus risk system of restrictions came into effect, but that it’s too soon to be certain.

A large chunk of northern England, including the major cities of Liverpool, Manchester and Sheffield, has been placed in the top tier of “very high” risk, with pubs closed and people from different households barred from mixing.

The regional disparities are causing friction between local politicians in the north and Prime Minister Boris Johnson’s Conservative government, which has been accused of not doing enough to support people and businesses hit by the local lockdowns.

The government is talking to local leaders in other areas, including the city of Warrington in northwest England and the central England county of Nottinghamshire, about moving into the highest tier.

Wales, Scotland and Northern Ireland have established their own public health rules, with Wales introducing the strictest measure: a 17-day lockdown for all its 3 million people.

Britain has Europe’s deadliest coronavirus outbreak, with almost 45,000 confirmed deaths.