Police said Monday they plan to check on 20,000 convicted sex offenders over the next 40 days, bolstering patrols in vacation spots across the country including the famous hiking trails of Jeju Island. The move was prompted by the grisly murders of a 10-year-old girl in Tongyeong, South Gyeongsang Province and a woman in the southern resort island.

Police normally check on convicted sex offenders every one to three months, but they merely verify their addresses and interview neighbors and have been criticized for being cursory.

The sex offenders on the radar are those who served more than five years in jail and whose offenses were committed less than 15 years ago, those who served more than three-year prison terms and whose offenses were committed less than 10 years ago, and criminals who were arrested more than two times over the last five years for sex crimes.

Police plan to resume investigating unsolved sex crimes and deploy more officers to search for missing women and children.