SEOUL, South Korea -- The United Nations' independent investigator on human rights in North Korea said Thursday he plans to examine North Korean claims that South Korea abducted 12 North Korean women.

Tomas Ojea Quintana said he raised the issue in a meeting with South Korea's vice foreign minister and requested that his government set up a meeting with the women, who had worked at a North Korean-run restaurant in China before coming to the South in April last year.

While North Korea regularly accuses South Korea of abducting or enticing its citizens to defect, Quintana said he was obliged to look into the case because his office has been gathering what seemed to be conflicting accounts of what happened. He didn't elaborate on the accounts.

He said he needed to be "exactly precise" about the women's situation and whether they decided to come to South Korea "according to their own will."

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"Parents of these women living in North Korea are claiming that their daughters were abducted, so all these factors oblige me to pay attention to the case and understand exactly what happened," Quintana said at a news conference in Seoul as he wrapped up a four-day visit to South Korea.

In response to Quintana's comments, South Korea's Foreign Ministry said the government had "sufficiently confirmed" the workers' "free will" in escaping from North Korea and resettling in the South. It wasn't immediately clear whether South Korea would allow Quintana to meet the workers.

The South Korean government has kept the workers' location secret and prevented the media from contacting them.

North Korea, which often makes extreme claims about defectors, insists that the workers were abducted by South Korean spies and has repeatedly demanded their return. South Korea denies the accusation, saying the workers chose to resettle in South Korea on their own. South Korea also rejected a highly unusual overture by North Korea last year to temporarily send the workers' relatives to the South to meet with them.

It was the largest group defection by North Koreans to the South since North Korean leader Kim Jong Un took power in 2011, according to South Korea's government.

South Korean officials earlier said North Korean-run restaurants overseas have been suffering economically because of strengthened sanctions in response to the country's nuclear weapons program. The workers who defected last year said their restaurant was struggling to meet demands from North Korean authorities for foreign currency earnings, South Korean officials said.

More than 30,000 North Koreans have fled to South Korea since the end of the 1950-53 Korean War, according to the South Korean government.

In September, the mother of a Japanese girl abducted by North Korea said she was thankful that President Trump had mentioned her in his U.N. General Assembly speech, and she hoped it could be a chance for a breakthrough. Megumi Yokota was abducted on her way home from school after badminton practice in November 1977.

Japan's government recognizes 17 of its citizens as abductees by North Korea, and Megumi, who was just 13 at the time, has become a symbol of a national movement to resolve the abduction issue.

North Korea, after years of denial, acknowledged in 2002 that its agents had abducted Japanese citizens to train spies in the 1970s and 1980s and eventually returned five of them. It said Megumi died and says others never entered North Korea, but Japan disputes that and is seeking further investigation.