Initial reports said that armed militants first fired rockets from a Nallah near the airbase and then tried to storm the complex but were repulsed by security forces.
TV channels reported that firing was going on and hand grenades were also hurled towards the airbase and airport - located in the west of the city.
"At least one attacker has been killed while three security personnel have been injured in the firing," a senior police official said.
Helicopters were circling in the air space around the airport and carrying out aerial surveillance.
In July, 10 terrorists had attacked the Karachi airport building, killing at least 29 people.
After the July incident, security was beefed up at all airports and airbases around the country.