Police believe cellphones are becoming a target of choice for thieves in central Auckland as they can be easily traded for drugs or cash.
Thefts of smartphones now account for up to half of all thefts in the city.
Inspector Andrew Coster said criminals are becoming more opportunistic, stealing phones from tables or handbags while their owners are distracted.
Some thieves are then approaching people in the street to sell them the stolen phones, generally for fairly small amounts of money.
He said police are working with phone companies to improve the reporting and blocking of stolen phones.