An anonymous benefactor has put up a $20,000 reward for information that brings the arrest and conviction of the coldhearted creep who packed a starving dog into a suitcase and tossed it into a Bronx trash bin.

The pooch, dubbed Fraggle by his rescuers, was receiving lifesaving medical treatment Saturday, said ­ASPCA spokesperson Natasha Whitling.

The 3-year-old pit bull was found at about 12:30 p.m. Thursday in a Dumpster at 700 Morris Ave.

Anyone with information is asked to call NYPD Crime Stoppers at (800) 577-TIPS.