NEWARK, N.J. — New Jersey’s largest city sued several opioid manufacturers, claiming they engaged in deceptive advertising practices and made false claims that “created a public nuisance” and unjustly enriched the companies.

Newark Mayor Ras Baraka announced the lawsuit seeking unspecified monetary damages on Friday. It alleges the companies downplayed the risk of opioid addiction and overstated the drugs’ long-term benefits.

The defendants misrepresented the risk of addiction “as modest, manageable, and outweighed by the benefits of opioid use,” the lawsuit alleges. The companies “continued to tell doctors and consumers that opioids could be taken in higher and higher doses without disclosing the ensuing risk to the patient,” according to the lawsuit.

One of the companies named in the lawsuit is Connecticut-based Purdue Pharma, makers of OxyContin. In an emailed statement, a Purdue spokesman said the company denies the allegations.

“We are deeply troubled by the opioid crisis and we are dedicated to being part of the solution,” spokesman Robert Josephson wrote.

According to the lawsuit, the majority of overdose deaths in Newark this year can be attributed to prescription or illicit opioids, and the drugs are a major contributing factor to rising criminal activity in the city.

“While opioids have been diverted through illicit prescribing and sales, it is the regular, legitimate prescribing of opioids that created and fueled this crisis,” the lawsuit contends.

On Thursday, the state attorney general’s office announced a lawsuit against Phoenix-based Insys Therapeutics, maker of a fentanyl painkiller spray. That lawsuit claims the company directed its sales force to have doctors prescribe the drug for any type of chronic pain even though it was only approved for cancer patients who couldn’t benefit from other opioids.