Big Island police said a 25-year-old Kailua-Kona man was knocked unconscious Thursday during a robbery at a shopping center in Kona.

Patrol officers responded to a call about 2:55 a.m. from the parking lot of a shopping mall between Kuakini Highway and Alii Drive in Kona.

The man told officers he had been at a Kona nightclub and was hit from behind while walking in the parking lot and knocked unconscious, police said.

When he woke up, his backpack was missing. The man refused treatment at the scene.

Police ask that anyone with information about the case call Detective Myra Iwamoto at (808) 326-4646, extension 281 or police at (808) 935-3511. Anonymous tips can be made to Crime Stoppers at (808) 961-8300 in Hilo or (808) 329-8181 in Kona.