[ILUG-BOM] image merging tool in linux

hi, i am looking for image merging software in linux (preferebly command line). i have a very big print which i have scanned into pieces (scanner size was not sufficient to scan at one go). i tried google, but no luck. tried gimp but it will have to do it manually i guess. but manually merging them border to border is not possible (due to insufficient RAM- even 2Gb is not enough, it stalls for some time even for a small movement of any image).

so it would be nice, simply to feed these images to a software and let it take whatever time to do the job. the similar software is present in many digital cameras, to be used to make panorama images.

any help is badly needed. thanks.