The advisory was issued by keeping in mind the extremist or militant activities in the region.

In a statement, the US Federal Aviation Administration (FAA) said: "The US warns its own air carriers to avoid Pakistan airspace due to risk of possible threat to attacks on US airlines (commercial and US state carriers) by Pakistan extremist and militant groups."

"The ongoing presence of extremist/militant elements operating in Pakistan poses a continued risk to the US civil aviation from small-arms fire and complex attacks against airports," the FAA said in its statement.

The FAA said some 'extremist/militant' groups are operating in Pakistan and are suspected of having access to man-portable air defence systems.

The FAA warned that there is a potential risk for extremists to "target civil aviation in Pakistan with MANPADS."