BROOKLYN - The NYPD is stepping up its patrols of the city's subway system due to a 17-percent rise in crime from this time last year.

According to police sources, more than 1,000 riders have been robbed since the beginning of 2011. They say thieves are targeting people near crowded trains who have electronic devices such as smartphones and tablets.

The NYPD says it's also adding more undercover officers, particularly on the weekends when most of the incidents occur. It's urging all subway riders to keep their phones and other devices in a hidden place and to be aware of their surroundings.

Hunt is on for suspect in subway robberiesThieves targeting iPhones, iPads in Brooklyn