According to the ever cheerful Debka,
"China Moves Forces into Afghanistan:
6 October: Before even the launching of the major US military offensive in Afghanistan, long Chinese convoys were carrying armed Chinese Muslim servicemen through northwest China into Afghanistan, according to DEBKAfile's intelligence experts.
They were sent in to fight alongside the ruling Taliban and Osama Bin Laden's Al Qaeda. Their number is estimated roughly between 5000 and 15,000. Our sources report another three convoys are behind the first 3000, who crossed the frontier Friday, October 5."