Toronto police have issued a public safety alert warning residents of the city of the dangers of selling and buying items online.

The alert was issued in light of an ongoing investigation into an armed robbery in the city's east end.

Police said a man advertising a necklace for sale on Kijiji was contacted by a prospective buyer. Over several days, the pair discussed the price and made arrangements to meet for the sale.

The seller met with the buyer on the street in the Strathmore Boulevard and Woodington Avenue, near Danforth and Woodbine Avenues.

The seller showed the necklace to the buyer, who then pulled a handgun from the waistband of his pants, police said.

The man pointed the gun at the seller, then stole the necklace and fled on foot.

In a statement Friday, police reminded the public to exercise caution when buying or selling items online.

"Police suggest all transactions should be conducted in a public place," the statement said.

The investigation into the theft is ongoing, and anyone with more information is asked to contact officers at 416-808-5400. Tips can also be left anonymously through Crime Stoppers at 416-222-8477 (TIPS).