Three 7-Eleven locations -- in Monrovia, San Gabriel and Azusa -- were robbed between 11 p.m. Thursday and 1 a.m. Friday, police said.
Those incidents followed a spate of robberies early Tuesday morning at 7-Elevens in Covina, Azusa and Glendora.
The at-large suspects are described as two clean-shaven black men, each about 5 feet 10 inches tall, between the ages of 20 and 25, wearing black pants and black hoodies. Authorities said the men should be considered armed and dangerous.
One of them asked clerks at the respective stores for cigarettes and then brandished a handgun, according to investigators.
At the 7-Eleven in the 5500 block of Azusa Avenue in Azusa, which has been struck twice this week, a surveillance camera captured Tuesday's incident on video.
About 12:44 a.m. Friday at that location, the pair of robbers confronted a clerk and stole approximately $500 before getting into a car and driving away, said a spokesperson for the Los Angeles County sheriff's San Dimas station.
Surveillance footage also shows the encounter at the San Gabriel store, located in the 800 block of Las Tunas Drive. In that incident, $200 in cash and two boxes of cigars were stolen, the San Gabriel Police Department said.
Anyone with information about any of the robberies is encouraged to contact the L.A. County Sheriff's Department at (909) 450-2700.