Artworks featuring President Trump and North Korean leader Kim Jong Un are displayed at a gallery during their summit on Feb. 28, 2019, in Hanoi. (Vincent Yu)

SEOUL — Just a month after hosting a summit between President Trump and North Korean leader Kim Jong Un, Vietnam has deported three North Korean refugees, sending them home via China to an uncertain future in their homeland.

The deportations mark a worrying new development for fleeing North Koreans, who previously had been safe if they managed to evade capture in China and reach a third country.

The deportations could also be an indication of North Korea’s growing diplomatic clout and lessening isolation since Kim stepped onto the global stage over the past year.

“I am worried that Kim Jong Un’s diplomatic engagement with Vietnam could have influenced them to deport North Korean refugees,” said Sokeel Park, South Korea director for a group called Liberty in North Korea, which helps North Korean refugees cross borders and adjust to life in the South.

But refugee groups also blamed South Korea’s government, amid reports it failed to respond promptly to a request to help the refugees after they were arrested in Vietnam. North Korean refugees in South Korea accuse the Seoul government of putting ties with Pyongyang ahead of human rights issues.

Aid workers told South Korea’s Chosun Ilbo newspaper that the South Korean Foreign Ministry failed to respond to a request to assist the refugees, a claim the ministry denied.

Three North Koreans who fled their country via China were arrested in the Vietnamese town of Ha Tinh on Monday, according to Chosun Ilbo. Aid workers who were assisting the refugees reached out to the South Korean Embassy in Vietnam and were told to contact Seoul’s Foreign Ministry directly.

The ministry repeatedly told them to wait, but no assistance was provided before the refugees were sent to China on Wednesday, the aid workers told Chosun Ilbo. China views North Korean defectors as illegal economic migrants and repatriates them to their home country, where they face severe punishment.

The Foreign Ministry in Seoul denied the report, saying in a statement that the ministry “immediately got in contact with the local authorities and took a stand against forcible repatriation to North Korea.” The ministry declined to comment on the safety and whereabouts of the refugees.

Han Jin-myung, a North Korean diplomat who served in Vietnam before defecting to South Korea in 2015, said the government in Seoul should have acted more quickly.

“Vietnam is in a tricky position, politically close to North Korea, and economically close to South Korea. Only the Seoul government can take the initiative to rescue those refugees,” he said. “Vietnam couldn’t have deported them if South Koreans promptly stepped in. It is irresponsible for the Seoul government to have let this happen.”

Vietnam has been one of Southeast Asian countries that provide safe haven for North Korean escapees, helping them reach South Korea.

"Once North Korean refugees make it through China, then they are normally safe,” said Park of Liberty in North Korea. “The fact that they were repatriated from Vietnam, after all that, is really concerning. . . . We don’t want this to set a precedent.”

The number of North Koreans coming annually to the South has dropped by half since Kim Jong Un came to power in 2011. South Korean lawmakers attribute the decline number to tighter border controls and China’s repatriation of refugees to North Korea.

Kim Sang-un, a North Korean refugee who reached South Korea, poses for a photograph in Seoul on May 18, 2018. (Jean Chung/For The Washington Post)