PORTLAND — Portland police are searching for a man who robbed gold and silver rings from a Congress Street store and threatened the 81-year-old shopkeeper with a knife.

A man wearing a blue hooded sweatshirt with a red mask covering his face robbed Ireland’s Crystal and Craft at 558 Congress St. at 5:15 p.m. Monday.

The man entered the store and pulled a knife on the store owner. When the owner tried to call police, the man yanked the telephone away from him, police said.

The man smashed a case and stole a number of rings, police said.

The owner ran to a nearby store and called police.

The suspect is described as about 6 feet tall, weighing 175 pounds and wearing blue jeans and a navy blue jacket over his sweatshirt.