SEOUL (AFP) - The UN's top expert on racism outlined on Monday "serious problems" faced by migrant workers and foreign marriage partners in South Korea, ranging from discriminatory exploitation and maltreatment to racist verbal abuse.

Following a week-long mission to Asia's fourth largest economy, during which requested meetings with ministers failed to materialise, UN Special Rapporteur Mutuma Ruteere said it was clear South Korea faced challenges related to its growing foreign community.

He called for better education, improved legislation - particularly on employment - and steps to ensure the media avoided "racist and xenophobic stereotypes." One of Asia's most ethnically homogenous societies, South Korea has a small but rising foreign population which has not always been made to feel welcome.

Some complaints focus on examples of racial insensitivity, such as performers wearing black-face on TV, or recent advertising for a new cigarette brand "This Africa" which featured chimpanzees dressed as a news anchor and a news reporter.

Others voice direct experience of overt discrimination, particularly migrant workers hired as low-paid, unskilled manual labourers.

Ruteere highlighted the plight of migrant workers in the agriculture and fishing sectors, who suffer tough working and living conditions, and generally work longer hours for less pay than their Korean counterparts.

As well as being denied their entitled share of the catch, non-Korean fishermen are "often subjected to racist and xenophobic verbal and physical abuse by ship owners and captains," he told a press briefing at the end of his visit.

He also noted that current regulations made it difficult for workers to change employment and many were forced to leave the country in order to be paid their severance settlement when their contract expired.

Together with migrant workers, the other main source of immigration is women - mostly from China and Southeast Asia - who come to marry South Korean men.

Ruteere said the marriage migrants often lacked adequate protection in the event of separation or divorce, especially when no children were involved.

They are "in a particularly vulnerable situation, as many are afraid to report domestic violence for fear of losing their residence permit," he said.

"You can see there are serious problems. They are problems that need attention by the authorities," he said.

Marriage migrants have forged a significant demographic change with the number of "multi-ethnic" children born to mixed marriages rising from just over 44,000 in 2007 to nearly 200,000 by 2013, according to government data.

In rural areas, where most mixed marriages take place, some projections suggest 49 per cent of all children will be multi-ethnic by 2020.

While Ruteere said he had not been informed of racist practices at the institutional level, he noted the existence of "xenophobic groups" who argue that policies supporting multicultural families discriminate against Koreans.

"It is important for the government to dispel these myths," he said.

Ruteere's report on his visit will be handed to the UN Human Rights Council in 2015.