RICHMOND -- Law enforcement officials say roving bands of youth stickup artists have helped drive up robberies in the area around the city's BART station, where lone pedestrians and commuters can be easy targets for street robberies.

"The Richmond transit center attracts commuters and travelers from all over Richmond," Richmond police Capt. Mark Gagan said. "We want them to be aware so they can take precautions ... robberies have become more frequent."

From Jan. 1 to May 1, police have recorded 18 robberies within a 1,500-foot radius of the Richmond BART station, up from 13 robberies over the same period last year.

On Tuesday, police say three teenage or young adult males robbed a victim in the 400 block of 19th Street around 11 p.m. One day earlier, suspects matching a similar description committed two robberies during the midnight hour, one in the 1700 block of Nevin Avenue and another in the 1400 block of Barrett Avenue. No injuries have been reported, but the suspects used a handgun in the attacks, Gagan said.

"They produce a weapon and demand personal items," Gagan said.

On the BART station property itself, which is within the jurisdiction of BART police, the spike is less pronounced, but crime overall is up in the past year, according to BART statistics.

In 2012, BART police recorded 43 property thefts and 10 robberies, according to BART police Deputy Chief Ben Fairow, up from 34 property thefts and eight robberies in 2011.

Fairow said he was unaware of any property crimes or robberies on the property in the past four or five weeks.

The uptick in crime around the BART station comes in the aftermath of a March 14 shooting that left one man dead near the BART entrance and sent rush-hour commuters scurrying for safety. The shooter was last seen running from the scene on the popular Metro Walk. He has not been caught.

Fairow said BART and Richmond police are working together to ensure the area is safe.

"Our system is quite safe. In general, the crime rate is lower in our stations than in the surrounding areas of more urban environments," Fairow said. "But I don't believe in hard lines between BART property and Richmond property. We are part of the community, and we are working together."

Gagan said the increase in robberies came to the fore April 15, when Officer Mitch Peixoto, who patrols the central Richmond beat around the station, sent an interdepartmental email alerting staff to the a trend of youthful-looking suspects committing armed robberies around the station.

Four youths, three age 15 and one age 16, were arrested on suspicion of committing robberies on April 12 and April 15, Gagan said. One duo is believed to have committed their crimes with a BB gun that looks like a semi-automatic pistol.

But even with those four off the streets, the crimes continue.

"They may be targeting people walking alone with ear buds or just generally unaware of their surroundings," Gagan said.

Gagan said Richmond police Chief Chris Magnus plans to meet with BART officials next week to discuss possible changes in the station's physical layout and how to ensure safety at a new parking structure scheduled to open this summer.

Contact Robert Rogers at 510-262-2726. Follow him at Twitter.com/roberthrogers.