Composite packing film and packing bag made of the same

A composite packing film, comprising a base aluminum foil or paper film having longitudinal and transverse elongations of not more than 10%,

• a layer of film elongated in one direction and laminated on one face of said base film through an adhesive,
• a layer of film elongated at least in a direction substantially perpendicular to the direction of elongation of said first elongated film, said second elongated film laminated to said base film on the side opposite said first elongated film, said first and second elongated films selected from the group consisting of high density polyethylene, polyesters, polypropylene, polyamides, polyvinyl alcohol, and mixtures thereof, and
• a layer of sealant having a melting point lower than the melting points of said first and second elongated films, laminated on at least one of said first and second elongated films on the side opposite said base film, said sealant selected from the group consisting of low density polyethylenes, ethylenevinyl acetate copolymers, ionomer resins, and mixtures thereof,
• characterized in that the difference between resistance against end tearing of said first elongated film and said second elongated film is at least about 15 kg, and the difference in thickness between the first elongated film and the second elongated film is at least about five microns.