SEOUL (Reuters) - China has resumed its ban on group tours into South Korea, South Korea’s inbound travel agency said on Wednesday, an issue that erupted last year as part of China’s retaliation over the South’s deployment of a U.S. anti-missile system.

“I was told from my boss this morning that our Chinese partners (based in Beijing and Shandong) said they won’t send group tourists to South Korea as of January,” the official from Naeil Tour Agency told Reuters by phone. The move was probably due to visa refusals by Chinese authorities, the official said.

The move came despite South Korean President Moon Jae-in’s recent visit to China, which showed some signs of a thaw in relations since the row over the anti-missile system broke out last year.