Police said the incident occurred outside a bank in Korangi area of Karachi.
"Four robbers tried to snatch cash from three men exiting the bank but they resisted. The robbers shot dead two of them and injured the third," police officer Mir Talpur said.
"As the robbers tried to flee after the shooting, a mob gathered and tried to capture them. Two of them managed to escape while a third took refuge in a shop and he was later rescued by us," he said.
"We are investigating the incident but we managed to save the robber who had taken refuge in the shop with great difficulty as the mob also wanted to deal with him," Talpur said.
This was not the first incident of mob justice in Pakistan's biggest city. Citizens fed up with increasing street crimes and robberies have taken the law into their hands several times in the past few years.
Some time ago, a mob lynched some men in the old quarters of Karachi when they tried to flee after looting a house.