[XeTeX] A strange error

[V. Sasi Kumar]

I have just started using XeTeX and am still to get used to debugging
source files. I just tried a test file containing two languages,English
and Malayalam and got the strange error message:

(./sample.tex
! Undefined control sequence.
l.1 \documentclass
                  [a4paper,10pt]{article}
? 

I understand that \documentclass is a genuine tex command. And I have
compiled latex and xetex files without problem earlier. Don't understand
why this error has suddenly appeared. Since this is the first line in
the document, it cannot be due to anything else in the document.

Any pointer to the problem would be appreciated.

Regards,
Sasi
-- 
V. Sasi Kumar
Free Software Foundation of India
http://swatantryam.blogspot.com