Singer G-Dragon will sue those who spread defamatory rumors about him online, the singer's attorney said a day after his drug test by the National Forensic Service (NFS) came back negative on Tuesday.

"We have collected evidence against those who have violated [G-Dragon's] rights, both through our own efforts and reports from fans, and are preparing to file reports against them to the investigative authorities," Kim Su-hyeon, an attorney at a law firm K1 Chamber, said in a statement on Wednesday.

"We will show no leniency," Kim added.

G-Dragon, whose real name is Kwon Ji-yong, tested negative in the thorough screening of his hair, toenails and fingernails conducted by the NFS earlier this week. A rapid urine test earlier this month also came back negative.

Drug tests using hair have the longest detection period among conventional testing methods, being able to trace drug use for up to a year, depending on the sample's length.

However, dyeing and bleaching hair may make it more difficult to detect drugs in hair samples. Fingernail drug testing has a detection period of up to six months.

Both came back negative for G-Dragon.

G-Dragon debuted as a member of the boy band Big Bang in 2006 under YG Entertainment. The band saw sensational success throughout the late 2000s and early 2010s. His exclusive contract with YG Entertainment ended in June.

He was previously questioned for alleged marijuana use in 2011 by the prosecution, but his indictment was suspended at the time after he confessed to having inhaled the substance unintentionally.

BY KIM JI-YE [kim.jiye@joongang.co.kr]