South Korean progressives on Thursday accused the government of caving into xenophobic sentiment by rejecting a plea for refugee status by hundreds of asylum seekers from war-ravaged Yemen, whose arrival on a resort island earlier this year triggered outrage.

Justice Party spokesman Choi Seok said South Korea was neglecting its responsibility as a member of the United Nations and letting public sentiment influence critical decisions on human rights.

"The Yemeni refugees have risked every danger to come to our country, just so that they could survive," Choi said.

"It's no different from the people of our own country half a century ago when they wandered around foreign countries as refugees through war and division. We should no longer ignore the voices of people who seek to live."

South Korea's Justice Ministry on Wednesday said it would not grant refugee status to nearly 400 Yemenis, saying instead it would issue one-year humanitarian stays to 339 of them.

The ministry rejected stay permits for 34 asylum seekers but said they could appeal, and postponed decisions for another 85 applicants, citing the need for further interviews.

The ministry previously granted temporary stays to 23 Yemenis.

The Yemenis arrived on the island of Jeju earlier this year, using an island tourist policy that allows foreigners visa-free entry for up to 30 days.

Thrown off by the flood of arrivals, South Korea excluded Yemenis from the no-visa benefits in June and banned the asylum seekers from leaving the island.

Since then, there have been a series of protests in Jeju and in the capital, Seoul, in which demonstrators called for the deportation of the asylum seekers, who are Muslims.

Protesters accused the Yemenis of being "fake refugees" who would steal jobs and pose a threat to local safety.

Anti-immigrant groups were quick to condemn the decision to grant the Yemenis temporary stays.

"We denounce the Justice Ministry for giving up on the safety of our people, being deceived by the fake refugees and saying they don't pose a terrorist threat," said Lee Hyeon-yeong, who helped organise a rally on Thursday in Seoul.

Other demonstrators held signs that read "Don't Be Like Europe" and "This Isn't Hate We Want Safety".

Though it was the recipient of large-scale international military and humanitarian interventions during the 1950-53 Korean War, South Korea has granted refugee status to only a fraction of asylum seekers since 1994, when it began accepting applications.

South Korea's culture greatly values ethnic homogeneity and people often guard fiercely against outsiders.

The Justice Ministry did not give a clear explanation of why the Yemeni applicants failed to meet its standards for refugee status.

An official from the Jeju Provincial Police Agency said on Thursday that four of the Yemenis were being investigated on suspicions that they consumed khat, a mild narcotic that is legal in Yemen but not in South Korea.

The police official, who didn't want to be named, citing office rules, said that the four Yemenis were among the 34 who were refused temporary stay.

The Yemenis who received the stay permits will have to reapply after their one-year term expires if they want to remain in South Korea.

The ministry said it could refuse to renew the permits if the situation in Yemen stabilises and becomes safe for the asylum seekers to return home.

Those who were granted temporary stays are allowed to leave Jeju for the mainland but must report their whereabouts to the immigration authorities.

The conflict in Yemen, the Arab world's poorest country, began in 2014 with the takeover of the capital by Houthis, an Iranian-backed movement that toppled the internationally recognised government.

A Saudi-led coalition launched to fight the Houthis has imposed sea, land, and air embargo while waging a devastating bombing campaign.

The conflict has left more than 10,000 civilians dead, driven millions from their homes and sparked a cholera epidemic.

UN officials have warned that millions more could very quickly become unable to feed themselves, while the rapid depreciation of Yemen's currency has caused food prices to rise at least 35 per cent.

Officials also fear a coalition-led assault on the Houthi-held port of Hodeida could shut it down.

Nearly 80 per cent of Yemen's imports come through the Red Sea city, including much of its humanitarian aid.