The Justice Ministry has vowed to strengthen the monitoring of electronic ankle tags following news that a sex offender cut the device off and went on to murder two women.

In a Monday briefing, the ministry announced a set of measures to prevent repeat offenses by those wearing monitoring anklets. The ministry's crime prevention chief Yoon Woong-jang first offered a deep apology to the victims of the latest murders and their families.

As for measures, anklets will be made with sturdier materials. So far they have been upgraded six times but the devices continued to be destroyed.

This year alone, 13 individuals broke them off as of August and two are still on the loose. The ministry will additionally beef up cooperation with police and local authorities to increase manpower for monitoring. 

It will also strengthen penalties for convicts that violate the electronic surveillance law, which carries up to seven years in prison or a 20 million won fine. But in reality, those charged have mostly received jail time of less than a year.