Gun-toting masked thieves have made off with a number of hand guns after holding up a camping and hunting store in Melbourne's north around lunchtime.

The thieves stormed the South Morang Hunting, Fishing and Camping store on Murdoch Road about 12.15pm on Tuesday.

Inside the South Morang camping and hunting store.

Three men armed with guns and a sledgehammer threatened staff before stealing several firearms, police said.

The trio fled in a waiting getaway car, driven by a fourth accomplice.

"No shots were fired in the robbery and the three victims were not injured," a police spokeswoman said.

Anyone with any information is urged to contact Crime Stoppers on 1800 333 000.