WOBURN, Mass. (AP) — Police and prosecutors are asking for help finding three robbers, two carrying handguns, who stole narcotics from a Walgreens pharmacy in Woburn and assaulted two clerks.

Middlesex District Attorney Marian Ryan and Woburn Police Chief Robert Ferullo said Thursday the men wore hoodies and covered their faces, but it's hoped someone will recognize them from surveillance video (http://bit.ly/K9maf3) and call Woburn police.

They said one man tied up a clerk at the front of the store Tuesday night while the other two went to the pharmacy counter.

One man held a gun to the pharmacy clerk's head and ordered her to open a locked narcotics cabinet, then held her down while they looted it. Police said the men stole the woman's wedding and engagement rings.

Police believe they fled in an older model, dark-colored Jeep Cherokee.