Chinese tourists in the U-shaped nine-dash line T-shirts arrive at Cam Ranh Airport in central Vietnam on May 13, 2018. Photo by Vu Cha

The travel agency that organized a local tours in May for a group of Chiense tourists who wore T-shirst with the controversial nine-dash line has been fined and its business temporarily closed.

Tourism authorities in Vietnam’s central province of Khanh Hoa handed out a nine-month suspension to the Vietnam Aladin Travel and Trading Company in the coastal resort town of Nha Trang and fined it VND42 million ($1,819) for allowing the tourists to wear offending T-shirts.

They said the nine-dash line represented a serious violation of Vietnam’s sovereignty over its waters and islands in the East Sea, known internationally as the South China Sea, Tuoi Tre newspaper reported.

"Due to the long suspension period which could lead to decreasing tourist sources and other issues, the company is going to shut down," a leader of the tour company said, adding that they have already paid the fine.

The punishment was handed out two months after 14 Chinese tourists were caught up wearing T-shirts with a nine-dash line, which claims most of the 3.5-million-square-kilometer South China Sea as China's territory, while checking in at the Cam Ranh International Airport.

The Chinese group was on a five-day visit to the coastal beach resort town Nha Trang which is an hour away.

Following the incident, the province's tourism department said it had met with all international tour companies to disseminate information about provisions of Vietnamese law relating to its sovereignty, and asked the latter to ensure compliance.

The T-shirt incident is only latest among a series of violations and egregious actions by Chinese nationals that Vietnam's tourism sector has encountered.

In other instances, Chinese acted as unlicensed tour guides themselves, spreading distorted versions of Vietnamese history, and Chinese people have opened shops that only accepted Chinese currency.

Nha Trang is one of the country’s top holiday destinations among both local and foreign tourists, attracting 750,000 foreign travelers to Khanh Hoa Province during the first quarter this year, of which 465,200 were from China.

The number of Chinese tourists to Vietnam skyrocketed 36 percent to a massive 2.58 million in the first half of this year, official figures show.