The announcement comes as 230 new cases of Covid-19 were registered by the State Serum Institute (SSI) on Monday, a continuation of an uptick in cases that began in the last week of August.
The three days from Friday to Monday saw a total of 566 new cases, SSI confirmed on Monday.
The number of hospitalised patients also saw a sharp increase in relative terms, moving from 18 to 29. Three people are currently in intensive care, with two on ventilators.
Nationally, over 1,000 cases have been recorded during the last week, the highest number since the spring. New cases have been detected in 82 of Denmark’s 98 municipalities, DR reports.
Copenhagen and Odense are among the 18 municipalities where the new restrictions will take effect. The remaining 16 municipalities all border or are part of greater Copenhagen: Frederiksberg, Tårnby, Dragør, Hvidovre, Brøndby, Vallensbæk, Ishøj, Rødovre, Glostrup, Albertslund, Høje-Taastrup, Gentofte, Gladsaxe, Ballerup, Herlev and Lyngby-Taarbæk.
In addition to the reduction of the number of people who may assemble in one place, new restrictions will be placed on bars, cafes and restaurants.
These establishments will now be required to close at midnight instead of 2am, as is the current national rule.
Odense and the Copenhagen area will also be excluded from plans to extend current provisions allowing fans to attend sports matches.
Health minister Magnus Heunicke called the current situation with the virus “the most concerning situation since the spring” at a press briefing on Tuesday afternoon.
The government has also requested schools, educational institutions and universities cancel all social activities.
Due to legal process, the restrictions will not take force until Wednesday, but the government has asked people in the relevant areas to begin following them immediately.
Copenhagen currently has an infection rate of 40 people per 100,000 residents for the last 7 days. However, cases in the capital are spread geographically.
That contrasts somewhat with Odense, where the outbreak has been linked to social activities at educational institutions.
53 new cases of Covid-19 in Copenhagen were registered on Monday, with 19 cases in Odense.
Heunicke rejected suggestions that infections were reaching an uncontrollable level and said that the restrictions represented “early response”.
Danish Patient Safety Authority director Anette Lykke Petri said meanwhile that 30 new cases of the virus had been traced to a single birthday party, DR reports.
Copenhagen Lord Mayor Frank Jensen encouraged young people in the city not to attend large parties and gatherings.
“Don’t go looking for these parties. Don’t go to them. You can be young, you can have a party, but don’t look for large parties,” Jensen said.