NEW YORK  —  Novel coronavirus cases are increasing among younger New Yorkers in their 20s, Mayor Bill de Blasio announced Monday. 

City residents between the ages of 20 and 29 saw COVID-19 rates rise in June — as Black Lives Matter protesters took to the streets and the economy began reopening — from less than 30 per 100,000 to a number nearing 40 per 100,000, de Blasio said. 

“We see a problem and we need to address it,” de Blasio said. “This disease is such a formidable foe, we cannot allow the slightest opening for the coronavirus.”

COVID-19 rates also increased, to a lesser extent, for New York City residents in their 30s between June 6 and June 27, spurring de Blasio to strengthen his recommendations for wearing masks. 

"New Yorkers should wear a face covering as much as possible around other people in an indoor setting that is not their home," de Blasio said. 

The mayor also noted the city’s COVID-19 labs had become overloaded in recent weeks as New York City increased its testing capacity to 40,000 per day. 

One reporter told the mayor he’d been waiting 12 days for a test without receiving results. 

“We’ve hit this log jam,” de Blasio said, and called on President Donald Trump to increase testing capacity on a national level. “We should be expanding testing on a much bigger scale.” 

This announcement came as a Siena College Research Institute researched a new poll showing 62 percent of New Yorkers fear the state has not yet seen the worst of the COVID-19 pandemic. 

While de Blasio celebrated New York City’s first 24 hours without a COVID-19 related death, he mourned the loss of 1-year-old Davell Gardner, who was shot to death in Bedford Stuyvesant late Sunday night. 

“It’s just horrifying,” de Blasio said. “I’m just heartbroken today.” 

Police did not have a person in custody as of about 9 a.m. Monday morning, de Blasio said. 

De Blasio faces city in turmoil over policing as weekend protests saw a New York Post reporter attacked by an Occupy City Hall protester and two pro-police marches in Brooklyn erupted in violence amid clashes with Black Lives Matter activists. 

Both sides are pointing the blame at City Hall, with social justice activists disappointed over a $1 billion cut to the NYPD budget they call “smoke and mirrors” and NYPD top brass arguing bail reform and Rikers Island releases have made the streets impossible to police. 

Trying to balance a thin line between appeasing both groups, de Blasio said the NYPD was overwhelmed and New Yorkers grappling with severe social and economic disruptions. 

“The criminal justice system is not functioning yet and we need it to,” de Blasio said. “Everything has been disrupted.”