South Koreans who were planning trips to China are having second thoughts on rising safety concerns amid heightening political tension between the two countries over Seoul's planned deployment of the THAAD missile defense system, sources said Tuesday.

A 35-year-old woman, asking only to be identified by her surname Kim, said she is deeply worried about whether she should stick to her plan to vacation in China. 

"I'm afraid because I don't know how bad the situation is there right now, but I've already paid for the airfare and all, so I think it's better that I went than canceling it, which will cost me a fee."

China is ramping up what appears to be a series of retaliatory measures against South Korea, after Seoul agreed to station a US anti-missile battery called the Terminal High Altitude Area Defense system on its soil in August last year.

The standoff between the two countries intensified late last month after Beijing ordered travel agencies in the country to stop selling trips to Korea, in response to a land swap between Lotte and the military here to build a site for the THAAD installation.

Lotte, South Korea's retail giant that depends heavily on China for revenue, has been hit hardest by a series of Beijing's hostile measures, with its nearly two dozen supermarkets placed under suspension as of Monday. It is also facing a possible boycott of its goods and services led by some aggressive groups of Chinese consumers.

On Monday, undated pictures of Chinese people staging an anti-Lotte protest and crushing stacks of bottles of a famous Korean liquor with a bulldozer were circulated via China-based social network services, spawning fresh concerns over growing anti-Korea sentiment in the world's second-largest economy.

Like Kim, many Koreans are now hesitant to visit China, according to local travel agencies, who said that they've been receiving a lot of calls from outbound travelers asking whether it's safe to go.

"Most of the calls were related to the safety issue, but that hasn't necessarily led to cancellations since calling off bookings incurs a fee," a travel agency official said.

About 4.4 million South Koreans visited China in 2015, accounting for the biggest portion of its foreign travelers, according to the Korea Tourism Organization. (Yonhap)