Two NATO helicopter gunships violated Pakistan's air space in its northwest border area Monday morning, reported local English TV channel Express.
According to the report, the helicopters penetrated into the Pakistani territory near Torkham and remained there for about five minutes before they returned to Afghanistan, Xinhua reported.
No firings have been reported.
Such incidents occurred several times in the last few months. Earlier this year, NATO helicopters entered the Pakistan's territorial sky, killing three Pakistani border soldiers while intending to attack some militant's hideouts on the Pakistani side.
This incident has led to a closure by the Pakistani government of a border pass for NATO convoys supplying goods and fuel to the U.S.-led NATO troops stationed in Afghanistan via Pakistan, leaving hundreds of NATO supply trucks stranded on the way, falling prey to numerous terrorist attacks.