Three nearby schools were evacuated, and local television showed police running with small children in their arms as shots rang out.
Millan said the shootout killed one armed man and wounded four officers, in the latest outbreak of violence across the border, located near San Diego, California.
Four armed men were reportedly arrested - one formerly a state police investigator and another a Tijuana police officer.
The four men will be flown to Mexico City for questioning.
In the past week, assailants shot and killed eight people in Tijuana, including two local police officers, as well as a district commander, his wife and his 12-year-old daughter.
Gang-related killings have risen in Mexico since the beginning of the year.
The government of Felipe Calderon, the Mexican president, has described the violence as "revenge" for its crackdown on organised crime.
In the central Mexican state of Hidalgo on Wednesday, assailants killed the director for public safety in the town of Tulancingo.
Jose Alvarado was shot more than 20 times, said Ahuizotl Figueroa, the Hidalgo state police director.