SEOUL, KOREA - South Korean sex offenders are to start wearing locally made electronic tracking devices around their ankles from next week, officials said Thursday.

The system will begin from September 1, alerting monitoring officials when offenders enter banned zones or violate their curfew, the Justice Ministry said.

Developer Samsung SDS said the gadget is 5.8 cm (2.3 inches) wide and 2.5 cm thick.

"Our product is smaller than similar devices used in other countries," a company official told AFP.

Electronic surveillance devices for sex offenders were first introduced in the United States in 1997 and are now used in about 10 countries, the ministry said.

?The system will help reduce sex crimes by putting sex offenders under close surveillance,? the ministry said in a statement.

About 300 convicted sex offenders are expected to wear the system for up to 10 years by the end of this year.

The country passed a law on the devices last year, after an 11-year-old girl was raped and killed by a neighbour in 2006.

Fears over children?s safety resurfaced earlier this year after the dismembered bodies of two elementary schoolgirls were found in the countryside.

They had also been killed by a neighbour.