The Oakland Police Department (OPD) says that they are getting an increased number of reports about armed robberies and carjackings that follow a similar pattern, and they were urging drivers to be "vigilant" and take steps to reduce their risk of being a crime victim.

It's fairly unsettling when a police department is essentially telling an entire city to "drive at your own risk" of being violently robbed or carjacked at any time. But without discussing specific cases, the department issued this public safety advisory on Wednesday.

"We are issuing this safety advisory to inform you of this alarming shift," the department writes. "We recommend our community members take precautions to keep themselves and their property safe. The crimes are happening across Oakland at various hours."

OPD does not say how many cases they are currently investigating, but they say, "In some recent cases, armed individuals intentionally collide their vehicles with the vehicles of [unsuspecting] victims in hopes of getting the victim to stop. In other incidents, the armed individuals block the victim's vehicle to prevent them from leaving."

Not all the incidents have been carjackings, apparently, but some have. And in others, the armed suspects just steal the victim's property before driving off.

"The Department is closely tracking this current trend, including descriptions of those responsible and their vehicles," OPD says.

In order to reduce the risk of being robbed, OPD is telling residents to "be vigilant and aware of their surroundings while driving and to report any suspicious activity immediately."

And, as for safety tips, they're kind of cold comfort but...

• Always keep your vehicle's doors locked and windows rolled up when driving, especially in high-risk areas.
• If you are involved in a vehicle collision and believe you are in danger, call the police immediately.
• If you are being followed or believe you are in danger, drive to the police station, or a well-lit and populated area and call the police.
• Do not be distracted by electronic devices.
• Be discreet with your property; this includes purses, phones, jewelry, and other valuables.

If you are a victim of a crime or have information regarding those who may be responsible for these crimes, you should call the OPD at 510-238-3326.

Photo: Justin Sullivan/Getty Images