A MAN who allegedly refused to pay his bill at a Perth restaurant was found with a sawn-off shot gun, ammunition and a balaclava inside his bag, police say.

Officers attended the William Street restaurant in Northbridge about 7pm on Monday and spoke to the man, who appeared agitated and was acting erratically.

The 33-year-old Warnbro man has been charged with several offences including possessing stolen property, possessing a firearm in circumstances of aggravation, stealing and breaching a violence restraining order.