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Mumbai's big surge came after a marginal drop in numbers. On Tuesday, the city recorded 809 new cases -- 113 less than Sunday -- and three deaths.
The spike rate has been very high in Mumbai, with cases registering a 188 per cent high in three weeks starting December 8.
In Delhi, the 50 per cent jump was reported hours after the city imposed a series of strict restrictions under the "Yellow Alert".
This was the biggest single-day spike since June 2 in Delhi. The positivity rate stands at 0.89 per cent -- the highest since May 31.
"We are disheartened when we see crowding at markets and malls. We will have to shut down markets if this continues," Chief Minister Arvind Kejriwal said. "I know you all are tired of restrictions, but it is important and there is nothing we can do about it," he added.
Under the new restrictions, schools, colleges and educational institutions, cinema halls and gyms will be shut and malls and shops will open on an odd-even basis within fixed hours.
Delhi Metro will run with 50 per cent seating capacity. Night curfew between 10 pm and 5 am has already started.
Maharashtra, meanwhile, recorded 2,172 new Covid cases and 22 deaths. The fatality rate in the state is 2.12 per cent. No case of Omicron was recorded on Wednesday. Till December 27, a total of 167 cases of the Omicron were detected in the state.
Maharashtra Health Minister Rajesh Tope has said fresh lockdown will be imposed on the state only if the demand for medical oxygen touches 800 metric tons per day.
Recently, the state government banned the assembly of more than five people in public places between 9 pm to 6 am and restricted the number of people allowed at public functions.
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