Ethnic gangs are sprouting up within their own communities across the country, particularly in the Seoul area, and in some cases, are linking up with Korean criminals.
Their nationalities are as varied as those of the foreigners living in Korea ― including Thai, Vietnamese, Pakistani and Chinese.
Police believe that these gangs have been preying on people of the same ethnic background, committing extortion, running illegal gambling pits, prostitution rings and meddling in small-time business disputes.
But, as indicated in cases in other countries, it may only be a matter of time before they grow in strength and expand beyond their own communities. There have also been signs that they are aligning themselves with Korean gangsters.
On Tuesday, Suseo Police in Seoul arrested seven Vietnamese men for kidnapping a Vietnamese woman and extorting $5,000 from her family in ransom. Of them, six were detained and the other was deported, police said.
Six of them arrived here in 2003 as industrial trainees while the other is a member of the "Hanoi Gang," officers said.
Police are widening their investigation after being tipped off that the Hanoi clan is funding their operations by running illegal casinos and exporting used vehicles.
The Gyeonggi Provincial Police Agency recently arrested a group of Thai gangsters for extorting millions of dollars from expats running businesses in Ansan, 30 kilometers southwest of Seoul, where the nation's largest expat community is located. Around 10 Thais were either beaten up or forced to pay protection money, police said.
In a separate case, a group of Vietnamese gangsters were caught last month for running illegal gambling houses and for extortion in satellite cities around Seoul. More than 14 Vietnamese people were beaten up or kidnapped for not paying money on time.
Police said they also extorted more than 160 million won ($128,000) from their families at home and abroad in exchange for their release.
According to the Supreme Prosecutors Office, the number of foreigners arrested was tallied at about 5,000 in 2000. It doubled to 10,000 in 2003. In 2008 alone, a total of 34,108 foreigners were caught.
In the latest crackdown between June and July in Gyeonggi Province, police arrested 1,836 foreign offenders.
According to the National Intelligence Service (NIS), those from Nigeria, Pakistan, China, Taiwan, Vietnam and Bangladesh account for the majority of foreign criminal groups across the country.
The NIS believes they collect funds by running illegal casinos and brothels, and by engaging in the drug trade and loan sharking.
Some of these ethnic gangs are forming ties with their Korean counterparts.
In March, a group of Vietnamese gangsters were arrested for hiring Korean prostitutes and selling drugs to native Koreans. Another group of Pakistani gangsters were caught smuggling 339 pieces of construction equipment worth 100 billion won ($80 million).
Police presume domestic crime syndicates pulled the strings from behind the scenes. Recently, police were tipped off that a Chinese gang based in Zirin, a province in the northeastern part of China, was looking for "Korean partners" to branch out here.
Criminal experts are divided over whether ethnic gangsters will expand beyond their own communities.
In an interview with a local media outlet, David Southwell, author of "the History of Organized Crime," said, "Throughout history and across every country where crime groups have sprung up from immigrant communities there are clearly visible, repeating patterns."
"At first these (illegal immigrants) will usually only be involved in preying on their own immigrant community through extortion, loan sharking, illegal betting, but with a solid base of criminal activity and income established, they will quickly look to expand into other areas. What these areas depend on is the organized crime set-up in the host country," Southwell said.
But professor Yang Kee-ho of SungKongHoe University, who is also vice president of an academy on multiracialism, opposes the view, saying, "Korea has its own unique immigration trends that keep foreign criminals from expanding into Korean communities.
"As seen in other countries, organized crime groups are usually created in closed, ghettoized communities, in which those from countries with similar cultural and linguistic backgrounds are crowded," Yang said. "Neither ghettoized foreign communities nor those alienated from mainstream communities have been reported. Also, the government has come up with various measures to embrace them and bring them to center stage. In this sense, I believe too much worry about foreign criminals expanding into Korean communities is unnecessary."