Rockets 'aimed at Karachi airport'

Pakistani police guard the area where the rockets were found

KARACHI, Pakistan (CNN) -- Pakistani police say they have found four rockets aimed towards the country's main international airport at Karachi, which is also used by Afghanistan's international security force.

The rockets were found in the open field of a neighborhood close to the airport in this southern port city, after a citizen tipped off the police.

A police statement released late Monday said the 107mm rockets were "placed on a wooden frame aimed in the general direction of the airport."

"An improvised timing device was connected to each rocket," it added.

The Associated Press has reported that two of the rockets were aimed at a terminal used by troops of the U.S.-led coalition. The other two were pointed at an airport hotel used as barracks by coalition forces.

The agency quoted Pakistani officials as blaming the attempted rocket attack on Islamic extremists.

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Authorities are investigating the incident and questioning people in the neighborhood.

The city's bomb disposal squad has defused the rockets.

The rockets were found two days after an incident in the same area, known as the Shah Faisal colony, in which a rocket was fired but did not cause any damage or injuries, police said.

Pakistan said last month the 17-nation International Security Assistance Force (ISAF) in Afghanistan had started using Karachi airport as a transit station for operations in the war-torn country.