Trang, owner of a travel agency specialized in South Korea tours, said that she has just canceled a tour of 26 customers because the South Korean embassy in Hanoi didn’t give them visas in time.

Her company suffered a loss of VND200 million ($8,620) from that tour alone as they have to compensate customers, she said.

The sudden surge in demand for South Korean visas in recent days has overloaded the country’s consular sections.

In recent days, thousands of people have been lining up as early as 3 a.m. at the embassy to get their visas, after rumors began circulating that a relaxed visa policy for Vietnamese citizens is going to be changed.

Dao Nguyen Xuan, representative of a Hanoi-based tour agency, said that her company has to pay in advance 30 percent of every ticket to South Korea, which is about VND6-7 million ($259-300). If visa approval gets delayed, her company will have to cancel the tours and lose its deposits, she said.

The embassy earlier this year increased the time for issuing visas for tour agencies from 6 days to 10 days, but companies say they are having have to wait even longer.

C-3 visa holders can stay in South Korea for up to 30 days, with no restrictions on number of visits for five years. Photo by VnExpress/Giang HuySome companies have even taken a chance and transported their customers to the airport in the hope that their visas will come in time, but this attempt has failed, forcing it to send customers back home.

With most customers booking South Korea tours in the summer, tour agencies said that if the current situation persists, their reputation will be damaged and they will lose customers.

These days, the consular department at the South Korean Embassy in downtown Hanoi gives out 300 tokens a day, but the number of people queuing up is estimated at around 3,000.

The South Korean government started issuing C-3 visas to permanent residents of Vietnam's three biggest cities Hanoi, Saigon and Da Nang, without insisting on occupational priority, as part of its "New Southern Policy."

C-3 visa holders can stay in South Korea for up to 30 days with no restrictions on the number of visits during the validity period of five years.

Park Jong Sun, head of the Korea Tourism Organization (KTO) office in Vietnam, said over 100,000 Vietnamese visited South Korea in the first three months this year, up 30 percent from the same period last year, with the relaxed visa policy for Vietnamese having an effect.

South Korea is one of the largest labor export markets for Vietnam. There were around 45,400 Vietnamese migrant workers in South Korea by the end of June 2018, the majority of them registered under the Employment Permit System, according to official labor reports.