Obama told churchgoers at the Vernon Park Church of God on Chicago's South Side that too many young lives are being claimed by violence and more must be done to combat the problem.

"From South Central L.A. to Newark, New Jersey, there's an epidemic of violence that's sickening the soul of this nation," the Illinois senator told the crowd. "The violence is unacceptable and it's got to stop."

Nearly three dozen Chicago students have been killed this year, according to Chicago Public Schools. Obama said that figure is higher than the number of Illinois serviceman who've died in Iraq in 2007.

"We need to express our collective anger through collective action," Obama said.

He said the government needs to permanently reinstate an assault weapons ban and close regulatory loopholes that protect unscrupulous gun dealers.