Thieves have been stepping up efforts to snatch purses and handbags hanging from the backs of chairs in many Washington restaurants and nightclubs, D.C. police said.

In an alert issued Tuesday, police warned that the city’s 2nd Police District, which includes the Georgetown area, recently has seen an increase in such crimes.

Those who have been stealing the bags or their contents are “very skilled,” police said, and seem to have practiced their larcenous techniques before applying them.

The thefts often are carried out by teams of people who coordinate their actions to distract customers and employees, police said.

In some cases, police said, their skill at diverting attention has enabled them to make off with wallets or smartphones while leaving the bags in place.

Usually, victims do not know what has happened until they prepare to leave and need to pay the check, the alert said.

Both the loss of credit cards and the possibility of identity theft inherent in the crimes “can be a continuing source of heartache for victims” long after the crime has taken place, police said.

Police said they are working to have restaurants suggest that patrons guard their property more carefully, and they are urging diners not to hang purses over chairbacks.