A clerk clobbered a robber in the head with a metal baseball bat, foiling an early morning robbery attempt at a Nevada convenience store, police said Wednesday.

"He whacked the guy good," North Las Vegas police Sgt. Tim Bedwell said.

The robber was knocked unconscious and hospitalized in critical condition with a serious head injury after the botched robbery just after 2 a.m., Bedwell said. He was not immediately identified.

The 52-year-old clerk and two customers escaped injury in the botched heist at the store about eight miles north of downtown Las Vegas.

The clerk also wasn't identified. But he told KVVU Fox 5 TV that he did what he thought he had to do to protect himself and his customers.

Bedwell said the robber displayed what appeared to be a gun, and the clerk complied with a demand to turn over cash and cigarettes before customers entering the store distracted the robber and the clerk swung the bat.

Investigators were checking whether the encounter was recorded by store video surveillance cameras, and Bedwell said police also were investigating whether the robber was responsible for other store robberies in the Las Vegas area.