SEOUL — Choi Jin-sil, a movie star, was the closest thing South Korea had to a national sweetheart.
So when Ms. Choi, 39, was found dead in her apartment on Oct. 2 in what the police concluded was a suicide, her grief-stricken homeland sought an answer to why the actress had chosen to end her life.
The police, the media and members of Parliament immediately pointed fingers at the Internet. Malicious online rumors led to Ms. Choi's suicide, the police said, after studying memos found at her home and interviewing friends and relatives.
Those online accusations claimed that Ms. Choi, who once won a government medal for her savings habits, was a loan shark. They asserted that a fellow actor, Ahn Jae-hwan, was driven to suicide because Ms. Choi had relentlessly pressed him to repay a $2 million debt.
Public outrage over Ms. Choi's suicide gave ammunition to the government of President Lee Myung-bak, which has long sought to regulate cyberspace, a major avenue for antigovernment protests in South Korea.
Earlier this year, the Lee government was reeling after weeks of protests against beef imports from the United States. Vicious antigovernment postings and online rumors on the dangers of lifting the ban on American beef fueled the political upheaval, which forced the entire cabinet to resign.
In a monthlong crackdown on online defamation, 900 agents from the government's Cyber Terror Response Center are scouring blogs and online discussion boards to identify and arrest those who "habitually post slander and instigate cyber bullying."
Hong Joon-pyo, floor leader of the governing Grand National Party, commented, "Internet space in our country has become the wall of a public toilet."
In the National Assembly, Ms. Choi's suicide set the country's rival parties on a collision course over how to regulate the Web. The governing party is promoting a law to punish online insults; the opposition parties accuse the government of trying to "rule cyberspace with martial law."
The opposition says that cyberspace violence is already dealt with under existing laws against slander and public insults. But the government says that a tougher, separate law is necessary to punish online abuse, which inflicts quicker and wider damage on victims.
To battle online harassment, the government's Communications Commission last year ordered Web portals with more than 300,000 visitors a day to require its users to submit their names and matching Social Security numbers before posting comments.
The police reported 10,028 cases of online libel last year, up from 3,667 reported in 2004.
Harassment in cyberspace has been blamed for a string of highly publicized suicides. Ms. Choi made headlines when she married a baseball player, Cho Sung Min, in 2000. But tabloids and Web bloggers were relentless in criticizing her when the marriage soured and she fought for custody of her two children.
TV producers and commercial sponsors dropped her. The general sentiment was that her career was over.
But in 2005, she made a comeback with a hugely popular soap opera called "My Rosy Life." In it, she dropped her cute-girl image and played a jilted wife who throws a kick at her errant husband, but reconciles with him when she learns she has terminal cancer.
This year, she broke another taboo by successfully petitioning a court to change the surname of her two children to her own.
But in an interview with MBC-TV in July, which was broadcast after her death, she said she "dreaded" the Internet, where posters had insulted her for being a single, divorced mother. The police said she had been taking antidepressants since her divorce.
In South Korea, volunteer counselors troll the Internet to discourage people from using the Web to trade tips on how to commit suicide and, in some cases, how to form suicide pacts.
"We have seen a sudden rise in copycat suicides following a celebrity death," said Jeon Jun-hee, an official at the Seoul Metropolitan Mental Health Center, which runs a suicide prevention hot line. Mr. Jeon said the hot line had received 60 calls a day, or twice the usual number, since Ms. Choi's suicide.