Attorney General Jeff Sessions says the Justice Department will crack down on violent gangs.

Sessions on Tuesday singled out one organization in particular, the MS-13 street gang. Its members are suspected in the killings of four people last week in Long Island. Sessions says in prepared remarks that gangs like MS-13 "represent one of the gravest threats to American safety."

He says tougher enforcement of immigration and border crimes will curb gang activity. And he says cities that protect people in the country illegally make efforts to fight gang violence more difficult. He says so-called sanctuary cities are "aiding these cartels to refill their ranks."

Sessions was speaking before a meeting with federal law enforcement officials to discuss ways to combat organized crime.