More than 50 people suspected to be linked to four smuggling rings have been arrested on charges of trafficking tons of gold bars in and out of South Korea, the customs office said Tuesday.

The Korea Customs Services said it has arrested six smugglers and booked 45 others without physical detention for violating the country's customs law.

The suspects are accused of breaking down 2,029 kilograms of gold bars, worth an estimated 97.5 billion won ($87.2 million), into small pieces; putting them in their rectums in China; and smuggling them into South Korea between March 2015 and April 2017.

Also, they smuggled out some 319 kg of the precious metal worth 16 billion won to Japan between March-September 2016.

It is the biggest gold smuggling case in history, with the total amount of confiscated gold reaching a record 2,348 kg, the KTS said.

The KTS noted that gold smuggling has been on a rise in recent years as criminal syndicates seek illegal profits on widening price difference of gold between South Korea and Japan amid rising worldwide demand for gold. (Yonhap)