I know that .mtl file containing textures is usually associated with .obj and Blender loads .mtl automatically (in most case scenarios) when corresponding .obj is imported. But is there any way to load such .mtl to .blend file or how can I work around this problem ?
The Obj file format is made of two files. The obj part contains the mesh informations. Geometry, UV mapping, normals. The mtl file contains a primitive Phong material, including existing paths to textures.
This material settings file cannot be loaded separately, it is tied to the obj file. And it does not contain textures, just paths to the textures. Embedding textures is not supported by the obj specifications.
But you can open the mtl file in any text editor. Have a look for the map kd entries. That's the paths to the textures.