Among the detained immigrants, 2,860 are from Southeast Asia and 83 from South Asia, said the public security ministry on Wednesday.
Most illegal immigrants were trying to sneak into Hong Kong from China to seek employment, it added.
Since the operation started on February 20, police in Guangdong, Guangxi and Yunnan provinces have dismantled three cross-border smuggling syndicates with the help of Hong Kong police, the ministry announced.
A total of 142 suspects from the three syndicates were apprehended by police, including 29 from countries in Southeast Asia and South Asia.
"Smugglers in Southeast Asia and South Asia recruit immigrants, smugglers in the mainland transfer them to Guangdong from the border and ports and then sneak them into Hong Kong, and smugglers in Hong Kong take control of the whole process," it added.
The authorities vowed to increase cooperation between police in Guangdong, Guangxi, Yunnan and Xinjiang and step up the joint crackdown on human smuggling, in an effort to safeguard social security and stability. (IANS)