Philadelphia police are asking for the public's help in identifying three men on surveillance tapes made during a robbery Sunday night at the Hess gas station at 2400 Castor Ave. in Kensington.

At least seven robberies in the Kensington area have been reported since Saturday, according to Sgt. Donna Bachmayer of East Detectives.

Bachmayer said one man on the tape could be a witness who could help identify the two men who entered the shop shortly after him. One of those men jumped the counter and put a knife to the cashier's head while the other pointed a gun at a second cashier.

The employees were ordered to empty the cash drawers, which they did, Bachmayer said.

Police believe four robberies on Saturday and two others on Sunday could be related to the Hess holdup. The Saturday crimes began at 12:01 a.m., when a man was robbed outside 3367 Coral St.; at 8:15 p.m. the Crispy Pizza shop at 1858 E. Allegheny Ave. was robbed; Santucci's at 4019 O St. was robbed at 10:30 p.m.; and at 11:15 p.m. the New Pizza shop at 2084 E. Allegheny Ave. was robbed.

On Sunday a grocery store at 3300 Mutter St. was robbed at 6:46 p.m. and a grocery at 4353 N. Fifth St. was robbed at 7:15 p.m.

Police said one of the robbers was 20 to 25 years old, about 5-foot-9, and 145 pounds. He was wearing jeans, a long, black, down jacket and a hooded sweatshirt with a skull or skeleton on the front. He carried a black revolver.

The other was about 17 to 20, 5-foot-6 to 5-foot-8, with a slim build and weighing about 120 pounds. He was wearing a black bomber jacket with a fur collar and a black knit hat that he sometimes pulled over his face.

The third man is a witness or possibly a third robber, about 20 to 25, 5-foot-9, about 160 pounds, with a round two-inch tattoo on the right side of his neck. Anyone with information is asked to call East Detectives at 215-686-3243.

Contact staff writer Barbara Boyer at 215-854-2641 or bboyer@phillynews.com.