Chinese troops have been stepping up security inspections along the border with North Korea in what seems to be a move to check up on tourists visiting certain sensitive regions, a U.S.-based media outlet said Wednesday.

An ethnic Korean source in Tumen, China, told Radio Free Asia that Chinese soldiers on border garrison have been reinforcing their security checks after North Korea vowed to retaliate against South Korea for the recent mass defection of North Koreans to the South.

In April, 13 North Koreans working at a Pyongyang-run restaurant in China defected and fled to the South shortly after the United Nations slapped toughened sanctions on the North over its nuclear bomb and long-range rocket tests earlier this year.

Pyongyang has accused Seoul of kidnapping the workers and demanded their repatriation. South Korea, on the other hand, insists the defectors came of their own free will.

The ethnic Korean source said that Chinese border inspections are being made under the pretext of protecting tourists visiting the Sino-North Korean border region, but the move is actually prohibiting foreign tourists from visiting the area.

A tourist guide in the city of Tumen also said the border troops belong to the Chinese People's Liberation Army.

Another source, who recently traveled to China and did not wish to be identified, told the RFA that the tourists spent a lot of time going through security inspections conducted by Chinese troops, saying, "We spent more time being checked than sightseeing."

The source added that armed soldiers came into the bus and examined passports, mobile phones and other belongings thoroughly. (Yonhap)