China has asked Vietnam to investigate reports that a border agent at Ho Chi Minh City airport defaced a Chinese citizen’s passport, scribbling the words “F*** you” on two of the pages and over maps of the contested South China Sea.

On Saturday, a Chinese woman surnamed Zhong from Guangzhou, claimed that she found the offensive words written in English on her passport, according to Chinese state media People’s Daily Online.

Zhong said upon entering Tan Son Nhat International Airport in Ho Chi Minh City, she handed over her passport to a member of the Vietnamese border staff.

“The border staff kept my passport for around three minutes and after I got it back, I saw ‘F…. you’ was scribbled on two pages where nine-dash line is printed,” Zhong was quoted as saying.

She added that she was disappointed by the actions of Vietnamese civil servants.

On Wednesday, the Chinese consulate in Ho Chi Minh City said in a statement it strongly condemned the “shameless and cowardly” act and asked Vietnamese officials to investigate and punish the agent.

Earlier this month, the Hague-based Permanent Court of Arbitration rejected Chinese exclusive rights to the South China Sea.

The “nine-dash” line which Beijing maintains claim over covers more than 80% of the disputed waters.

Brunei, Malaysia, the Philippines, Taiwan and Vietnam have rival claims.

– with other agencies