# Path of includegraphics is relative - but to what?

I am trying to include graphics for a document. The arborescence is as follows:

+ REPORT
+-- RESOURCES
|   + icon.png
+-- TEX
+ report.tex
+ report.cls


The report.tex starts with {report}, and the report.cls file has the following lines :

\RequirePackage(graphicx)
[...]
\includegraphics[...]{../RESOURCES/icon}


Now, when I run pdflatex on that .tex like this, everything runs smoothly :

> pdflatex report.tex


However, when I run it from another directory, it seems to me that the "relative" path is taken as "relative from the execution directory" and not "relative from the .tex file".

> pdflatex TEX/report.tex
[...]
!pdfTex error : pdflatex file {../RESOURCES/icon.png} : cannot find image file


This seems to be confirmed by this answer.

I tried using \graphicspath{{../RESOURCES/}} before my \begin{document}, but it wasn't successful.

So, my question is : is there any way of having relative paths in .tex regarded as relative to the .tex rather than to the execution dir when using pdflatex?