ALAMEDA -- A man armed with a handgun confronted a woman as she walked through Alameda South Shore Center on Sunday afternoon, stealing her $600 necklace before running away.

The 51-year-old woman, who lives in Alameda, was not hurt during the robbery, which occurred just before 1 p.m. in a walkway near Starbucks at the shopping center, police said.

The man was last seen running toward the U.S. Post Office on Shore Line Drive, Alameda police Lt. Ted Horlbeck said Monday.

Investigators are not linking the case with another robbery at the center on Sept. 11, when a man stole a 14-year-old girl's cell phone at gunpoint, since the suspect descriptions are different.

The victim on Sunday described the robber as an African-American man, 20 to 25 years old, 5-feet 10-inches to 6-feet tall, weighing about 180 pounds. He was wearing a black hoodie and dark pants, the woman said.

Alameda police ask anyone who has information to call 510-337-8340.

Reach Peter Hegarty at 510-748-1654 or follow him on Twitter.com/Peter_Hegarty/.