The Boston Police Department is issuing a warning after a string of recent cellphone thefts targeting people leaving nightclubs and bars in the city late at night.

Police said the recent incidents have been reported in the Downtown, Back Bay, Fenway, and Seaport neighborhoods of Boston.

According to police, the thefts have been reported mostly between about 11:30 p.m. and 2 a.m. 

Police said that as part of the string of thefts, the suspects steal phones during or after ride shares, by offering unsolicited rides, and by making physical or verbal threats of violence. In the past, suspect have also pickpocketed victims, police said.

Suspects have also "shoulder surfed," police said. That tactic allows them to watch victims put their passwords into their phones. The suspects then ask to borrow phones or to exchange information, sometimes asking victims to take a photo for them.

"Once in possession of the phone, suspects have accessed sensitive information and made unauthorized transactions using financial apps," Boston police said. "Targets have included Apple ID accounts, Apple Pay, Venmo, Cash App, PayPal, cryptocurrency wallets, and sports betting apps like DraftKings. In several cases, credit and debit cards have also been used fraudulently."

The best way people can protect themselves, police said, is to remain vigilant, use strong security settings on cellphones, and avoid handing devices to strangers under any circumstance. 

Police did not specify how many reports of cellphone thefts they have received.

Anyone with information is asked to contact the Boston Police Department.