The number of drug offenders grew more than 5 percent on-year in 2013, with the amount of confiscated narcotics soaring over 30 percent, data showed Tuesday.

According to the data compiled by the Supreme Public Prosecutors' Office, the number of people arrested for drug-related crimes came to 9,764 last year, up 5.5 percent from a year earlier.

The total number of drug offenders had been on the decline since 2009 with the authorities cracking down on 11,875 people that year, followed by 9,732 in 2010 and 9,174 in 2011, according to the data.

But the figure swung to an upturn in 2012, when the number of people busted for drug offenses edged up 0.9 percent on-year to 9,255.

The number of foreign offenders -- including foreign manual workers and American soldiers -- came to 381 last year, a 6.1 percent increase from 359 a year earlier.

The authorities confiscated a total of 65.7 kilograms of illegal drugs between January and November last year, up 30.3 percent from the previous year's 50.04 kilograms.

The amount of confiscated cocaine surged nearly 18 times on-year to 1.2 kilograms last year, with that of methamphetamine skyrocketing 82 percent to 37.7 kilograms.

The amount of seized marijuana also increased some 8 percent to 23.4 kilograms last year, according to the data. (Yonhap News)