The U.S. Justice Department has filed a lawsuit accusing Walgreens of filling millions of prescriptions for Americans over the last decade and more without a legitimate purpose, including for dangerous amounts of opioids.

The U.S. Justice Department said on Friday it has filed a lawsuit alleging that pharmacy chain operator Walgreens knowingly filled millions of prescriptions that lacked a legitimate medical purpose.

The Department of Justice sued pharmacy giant Walgreens for allegedly dispensing millions of unlawful prescriptions. Walgreens from August 2012 until the present "knowingly" filled those prescriptions, which "lacked a legitimate medical purpose, were not valid, and/or were not issued in the usual course of professional practice," the DOJ said.

The Department of Justice says Walgreens has dispensed millions of unlawful prescriptions over the years. Walgreens contends the government is trying to enforce rules "that don't exist."

The pharmacy chain since August 2012 filled prescriptions that lacked a legitimate medical purpose, were invalid or weren’t issued in professional practice, the Justice Department said.