كتب : Hatem Maher
Al-Qahtani posted three goals in the third, 21st and 58th minutes to hand Saudi Arabia their second win in the qualifiers.
The result put Saudi Arabia on top of Group A with six points, ahead of second-placed Japan, who beat Yemen 2-0, on a goal difference.
In Group D, Australia grabbed their second successive win after beating Kuwait 2-0 in Sydney.
Travis Dodd put Australia ahead in the 76th minute before Sasho Petrovksi sealed the victory ten minutes later.
Australia are leading their group on six points, five ahead of Bahrain and Kuwait.
The other Group D match between Bahrain and Lebanon has been postponed due to Israel-Lebanon war.
Elsewhere, Qatar are on the brink of reaching the 2007 AFC Asian Cup after thrashing Bangladesh 4-1 in a Group F match.