South Korean police reported over 20,000 criminal cases involving foreign nationals last year and witnessed increases in drug-related crimes and frauds by foreigners, Yonhap News Agency reported Wednesday, quoting a report.

According to data released by the National Police Agency (NPA), 20,623 foreigners were detained on criminal charges, including murder and robbery, along with more minor crimes, in 2008, marking a steep rise from 14,524 in 2007 and 12,657 in 2006.

The corresponding figures for 2003 and 2004 stood at 6,144 and 9,103, respectively.

The number of foreign nationals accused of being involved in drug-related crimes tripled to 694 last year from 231 in 2007. In 2006, the number of foreigners detained on drug charges totaled just 73.

NPA data also found that 85 foreigners were indicted for murder in 2008, up from 54 in 2007 and 32 in 2003.

The number of convicted rapists who were foreign nationals totaled 114 last year, the same as in 2007. The corresponding figures for 2006 and 2003 were 68 and 49, respectively.

The rising number in criminal reports involving foreigners was attributed to an increase in the resident foreign population and visitors to Korea in recent years, NPA officials said.

They also noted that eased customs controls intended to promote the nation's tourism and trade sectors have left loopholes.

According to the country's immigration bureau, some 1.15 million foreigners were living in South Korea as of December last year.

"Under the nation's current immigration system, it is possible for deported foreign criminals to come back to South Korea with their name changed," said Park Wan-seok of the Alliance for Coping with Foreign Laborers, a civic group.