Seoul, South Korea (CNN) Hundreds of mourners took to the streets of Seoul Saturday to remember a mother who fled poverty in North Korea , only to die of suspected starvation in her small apartment in South Korea. Mourners, mostly defectors themselves, marched with two symbolic empty caskets to the Blue House, South Korea's presidential office, eventually clashing with the police.

"Bring back our Sung-ok!" they chanted and demanded an apology from President Moon Jae-in, himself, for what they see as neglect of defectors' welfare.

The water inspector called the police, who found two heavily decomposed bodies and an empty fridge, leading the police officer to note starvation as the suspected cause of death, according to a statement from Gwanak district police. An autopsy was inconclusive as the bodies had decomposed.

Protesters demanding a government apology for the deaths of Han Sung-ok and Kim Dong-jin clash with the police.

The case has become a lightning rod in South Korea, where some are arguing that the government is doing little for the thousands who have fled the repressive regime in North Korea. They want to see a thorough investigation into Han and her son's death and policy changes to prevent future tragedies.

Although there are no official statistics showing exactly how many North Koreans have fled their country, South Korea says it has welcomed more than 32,000 defectors since 1998, including 1,137 defectors last year alone. North Korea is home to about 25 million people.

Earlier this month, South Korea's Unification Ministry publicly apologized and proposed comprehensive measures to "minimize blind spots in welfare," including a survey of all defectors in South Korea to find those who are at risk and increased information sharing between government agencies.

But North Korean defector activist groups want more changes.

"It's our position that this tragedy must never be repeated," Heo Kwang-il, the chairman of North Korean Defectors Emergency Response Committee, a committee formed by defector interest groups following Han's death, wrote in a statement released earlier this month.

A hard life and a tragic death

Han did not live an easy life.

She left North Korea in 2007, according to the defectors' emergency committee. Han was then sold to her Korean-Chinese husband who lived in China, according to Kim Yong-hwa, a defector activist who has known Han for a decade and who helped bring her to South Korea.

According to a report by the London-based non-profit organization Korea Future Initiative, thousands of North Korean girls and women are abducted or trafficked to work in China's multimillion-dollar sex trade.

Kim met Han at a safe house in Shenyang, a city in China's northeast Liaoning province, which borders North Korea. Four years later, the pair met again in Seoul where Han was picking up second-hand clothes from Kim's office for her and her husband to wear at their new jobs at a shipyard.

After South Korea's shipbuilding industry crashed in 2015, Han's husband lost his job, and Han was unable to work as she had a newborn to look after, Kim said. The family moved back to China looking for better opportunities.

In December of last year, Han called Kim to tell him that she had divorced her husband and moved to Seoul with her son. Kim helped them find a public apartment. Because her son had epilepsy and needed round-the-clock care, she was unable to work and asked for Kim's help accessing monthly welfare support.

But Han's welfare application was denied as she didn't have divorce papers and medical examination papers, Kim said. A government official from the Welfare Office told CNN that it had no record of receiving a phone call about Han's claim, although it did have a record of her visiting the office last year.

Six months later, Han and her son were dead in the apartment Kim had helped find for them.

"I couldn't do anything for her," said Kim. "Why did I bring her here from her farm? Even in rural China, one doesn't die of starvation."

A wider problem

Although South Korea does provide support to North Korean defectors, some believe they could do a lot more.

When defectors reach South Korea, they are given 8 million won ($6,704) cash. Two-person households also get unconditional welfare support of 870,000 won ($729) per month for six months, less than the country's average median income for a two-person household, which is 2.9 million won ($2,430).

Still, many defectors -- like Han -- struggle to find employment. A survey last year by South Korea's Unification Ministry of more than 25,000 defectors found their rate of unemployment is 2.9% higher than South Koreans. Almost 60% of those surveyed said that childcare obstructed their ability to gain employment.

This was true for Kim Jeong-ah, another defector who never met Han, although the two women attended a compulsory re-education center near Seoul at the same time.

Photos of Han Sung-ok and Kim Dong-jin are displayed at a protest in Seoul after their deaths.

Like Han, 43-year-old Kim was sold as a bride in China. Kim Jeong-ah came to Seoul alone 13 years ago. She later had a child -- and when she left her child at daycare so she could look for work, a welfare officer told her that her support would be cut off the same day she used daycare.

"I cannot go to job interviews with my child on my back," she said.

A government official from the Welfare Office in Gunpo City, where Kim lives, said a person needed to spend all day watching their child to be eligible for child welfare support.

Kim Jeong-ah has only found part-time work giving occasional lectures and TV appearances on North Korea. She lives in a tiny, subsidized apartment in Seoul with her husband and son.

On top of the welfare issues, Kim Jeong-ah says South Koreans often aren't aware of the psychological trauma many defectors are dealing with. Because of that, she wants to see more funds given to defector interest groups that are led by defectors themselves.

"That pain is only communicable with other escapees who carry the same," she said. "We can never forget."