SEOUL (Reuters) - Several North Korean waitresses who arrived in South Korea in 2016 in a group of 13 defectors have said they were coerced into leaving, and a South Korean ministry that handles ties with the North said on Friday it was trying to verify their account.

The defection of 12 waitresses and their manager from a North Korean restaurant in China was one of the biggest mass defection cases involving North Koreans in years.

South Korea said at the time they had defected out of admiration for South Korean society. North Korea denounced it as a “hideous” abduction of its workers and demanded them back.

Evidence that at least some of the 12 waitresses did not come freely, revealed in a television program aired on Thursday, comes at a sensitive time.

After a year of sharply rising tension and fears of war over North Korea’s defiant nuclear and missile tests, inter-Korean relations have improved dramatically this year.

The two Koreas held their first summit in years in late April. North Korea and the United States are due to hold their first ever summit in Singapore on June 12.

Four of the 12 waitresses from the Ryugyong Korean Restaurant in China told the South Korean television network JTBC they had been forced to give their written consent to defect inside the South Korean embassy in Malaysia after being threatened by their manager.

“If we didn’t sign our names, he threatened he would turn us over to the security police in North Korea for watching South Korean television dramas and I had no choice,” one of the women said.

“I wish I could take that decision back.”

North Korean defectors often cross China into Southeast Asia before trying to reach South Korea.

South Korea’s announcement of the defections at the time was unusual. Authorities usually keep such matters quiet.

Critics said the government was trying to win favor with voters in parliamentary elections that came days after the defections were announced. The government denied that.

None of the women was identified, and the television network blurred their faces. Reuters was unable to contact any of them.

They said they had been unaware of their final destination until they found themselves at the embassy in Malaysia.

The restaurant manager, Heo Gang-il, told the television station he had been working with South Korean intelligence agents and had threatened the women if they did not join him in defecting.

Heo said he had lied to the women about their destination, adding he was speaking out after the South’s National Intelligence Service (NIS) failed to keep a promise to give him a job and a medal.

The NIS declined to comment.

Baik Tae-hyun, a spokesman for South Korea’s unification ministry, which handles issues involving North Korea, told a briefing the account from the North Koreans had to be checked.

But he said the ministry had had difficulty reaching them as the NIS had handled their resettlement.

“We have tried to set up interviews with these defector waitresses,” said Baik in a regular media briefing.

“However, there was a limit as to how much we could assess their statuses as these people did not want meetings (with the ministry),” he said.