A growing number of cities in France are experiencing a worrying spread of the coronavirus and will have to enact new restrictions on public gatherings, the French health minister said on Thursday as he urged people to reduce their social contacts.

Olivier Véran, the minister, said at a news conference that local authorities in the cities of Lyon and Nice plan to tighten restrictions in the coming days, and he warned that other cities like Paris, Dijon or Toulouse might have to do the same soon.

“The epidemic is once again very active in our country,” Mr. Véran said.

France’s rate per capita of new cases over the last seven days is currently one of the highest in Europe, with 91 cases per 100,000 residents, up from 10 at the end of July. Gatherings of family and friends had become “massive” vectors of infections, Mr. Véran said.

In cities like Marseille and Bordeaux — where the number of cases has surged the most, and where authorities had limited public gatherings to 10 people last week — Mr. Véran said authorities might have to close bars and restaurants or ban gatherings completely.

Mr. Véran said that France had carried out over 1.2 million tests over the past week, but he acknowledged that massive demand had led to long lines and growing waiting times. Hundreds of medical lab workers even went on strike on Thursday over strained working conditions because of the overwhelming demand. Mr. Véran said the authorities were improving the process, while working on rolling out faster antibody tests and greenlighting saliva tests.

Mr. Véran also said that the authorities were able to monitor the pandemic much more closely than they could in the spring and that doctors have improved at treating severe cases of the virus.

“We are not fighting with the same weapons and we know our opponent better,” Mr. Véran said.

Reporting was contributed by Peter Baker, Aurelien Breeden, Luke Broadwater, Nick Bruce, Emily Cochrane, Stacy Cowley, Hana de Goeij, Elizabeth Dias, Sydney Ember, Nicholas Fandos, Emma G. Fitzsimmons, Jeffrey Gettleman, Denise Grady, Anemona Hartocollis, Jan Hoffman, Mike Ives, Jennifer Jett, Apoorva Mandavilli, Alex Marshall, Claire Cain Miller, David Montgomery, Claire Moses, Roni Caryn Rabin, Livia Albeck-Ripka, Anna Schaverien, Nelson D. Schwartz, Christopher F. Schuetze, Michael D. Shear, Eliza Shapiro, Daniel E. Slotnik, Mitch Smith, Kate Taylor, Katie Thomas, Glenn Thrush, Maria Varenikova, Lauren Wolfe and Sameer Yasir.