The announcement follows a sudden increase in demand for South Korean visas in Vietnam.

The Hanoi office will open on April 25 at Discovery Building, 302 Cau Giay Street in Cau Giay District, and the embassy is working on opening the HCMC office.

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.

In December 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.

A surge in visa applications in Hanoi in a short period is causing problems, the KTO said. Many travel companies have had to cancel tours because visas are not coming in time.

Following rumors that the visa policy could change any time, thousands have been thronging the South Korean embassy in Charmvit Tower on Tran Duy Hung Street since last month.

Many are queuing up from 2-3 a.m. to get a token number and await their turn.

Most are from outlying districts in Hanoi and north-central provinces such as Nghe An, Ha Tinh and Thanh Hoa, traditionally big source of labor for South Korea.

The consular department only gives out 300 tokens a day, but the number of people queuing up is estimated at around 3,000.

Applicants have to pay a fee of VND1.8 million ($80) and wait for a week to be considered for a five-year visa, while professionals like doctors and lawyers and students enrolled in programs of four years or more in South Korean universities and those with masters’ degrees and above from overseas are eligible for 10-year multiple-entry visas.

South Korea is one of the largest labor export markets for Vietnam. There were over 45,398 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.