Campaigners are calling on a witch-hunt for gay soldiers to end immediately.
According to campaign group the Military Human Rights Center for Korea (MHRCK), General Jang Jun-kyu, army chief of staff in South Korea launched a “track-down process” to find and out suspected gay personnel.
This included setting up fake profiles on dating apps to track down soldiers and expose them.
The process is thought to have identified 50 soldiers, 20 of whom now face charges under the country’s military anti-homosexuality laws.
Kyle Knight, a researcher in the LGBT rights programme at Human Rights Watch, accused South Korea’s government of hypocrisy.
He says it the government had “consistently voted to support measures at the United Nations that call for an end to discrimination against LGBT people, but has failed to uphold those principles at home”.
Although same-sex sexual activity is not illegal in the country, the army retains a code of conduct that bans homosexuality, and military service is mandatory.
Under South Korean law a soldier who commits “sodomy” or “other disgraceful conduct” can face up to two years in prison.
The country’s presidential front-runner, Moon Jae-in, shocked LGBT rights activists when he declared that he is opposed to homosexuality.
“I oppose,” Mr Jae-in said, when asked his view on homosexuality, Associated Press has reported.
Jung Yol, a gay rights activist, said: “Moon needs to offer an apology and a correction of his comments made on live television.”
“What he said was clearly hate speech, and since he is the candidate favoured to win the election, his words can influence how people think.”
The South Korea Times has since written that the election has exposed socially conservative attitudes in the country.
“Moon was a human rights lawyer and hearing him say that he was against a minority because of their sexual orientation was nothing short of shocking,” the newspaper wrote in its editorial.
“Sexuality should be left to the discretion of an individual, and members of the LGBT community should have their rights protected just like any other minority.”
Students have begun brandishing “Arrest me, too” signs on university campuses across South Korea following the reported arrests of gay and bi serving soldiers.
A poster appeared at one South Korean institution, Sungshin Women’s University, reading: “If gay soldiers are criminals, then the women’s university campus couple were also criminals. So arrest us, too.”
Another university poster reads: “I’ve had to listen to the presidential candidate who is likely to win the election saying, ‘I don’t support homosexuality, but it shouldn’t be punished. But I won’t enact anti-discrimination legislation.’
“Meanwhile, activists who travelled there to get an apology were arrested.”
13 people were detained following the protests, with some dragged away, according to LGBT rights group Solidarity for LGBT Human Rights of Korea.