The move came after regional health and local authority leaders engaged in two days of talks.
What are the rules and restrictions in Birmingham?
The ramped-up rules mean a ban on different households meeting indoors in the three areas - except for those in a support bubble.
Birmingham City Council confirmed people could still go out to shops, restaurants and other venues, in a maximum group of six from more than one household, but told people to be "vigilant".
What are the new rules in Birmingham, Sandwell and Solihull?
From Tuesday, residents in Birmingham, Sandwell and Solihull must not:
Host people they do not live with in their home or garden, unless they’re in their support bubble
Meet people they do not live with in their home or garden, whether inside or outside of the affected area, unless they’re in their support bubble
He said: "This is about mixing between households, it is not about prevention of schools, workplaces, transport, any of the other options."
Explaining where the new measures will apply in Birmingham, Cllr Ward said: "From Tuesday September 15, Birmingham residents will not be able to mix with any other households, indoors or in private gardens, except for those in a support bubble.
"This restriction will apply both inside and outside the city boundary.
"If you live in the city boundary, you cannot mix with another household outside the city boundary.
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"If you live in the affected area, in order to help prevent the spread of Covid-19, you must not host people you do not live with in your home or garden, unless they're in your support bubble."
He added: "You must not meet people who do not live with, in their home or garden, whether inside or outside of the affected area, unless in your support bubble."
Has there been a rise in cases?
According to NHS Digital data, the seven-day rate for the city to September 8 showed 78.2 cases per 100,000 with 892 cases over the period - among the highest in Birmingham since April's peak.
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For the previous seven-day period, the rate was just over 30.
Solihull's latest infection rate for the week ending September 8 was 62.8 per 100,000, while Sandwell has battled with stubbornly high infection rates for weeks.
Bolton's seven-day rate currently stands at 192 cases per 100,000, and Sunderland is on 84, according to data from NHS Digital.
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Speaking of a potential lockdown in the area on September 10, Health Secretary Matt Hancock said: "We are seeing some sharp rises in cases across many parts of the West Midlands.
"And so we do take these decisions on a localised basis."