SEOUL, Feb 3 (Reuters) - South Korea's President Moon Jae-in called on Wednesday for seamless preparations for coronavirus vaccinations, as regulators approved imports of Pfizer's COVID-19 shot and the country prepared to begin inoculations later this month.

Despite initial success in taming earlier outbreaks, South Korea is grappling with its third and largest wave of infections, which has fuelled criticism that the government was slow to secure vaccines for its population of 52 million.

The special regulatory approval on Wednesday will allow South Korea to receive 117,000 doses of the Pfizer /BioNTech vaccine via the COVAX global vaccine sharing scheme around mid-February, drug safety minister Kim Gang-lip told a news conference.

The country has yet to approve a COVID-19 vaccine, but gave the regulatory clearance for emergency imports so it can kick off inoculation campaigns later this month, starting with about 50,000 frontline health workers.

The government had said it will inoculate about 10 million high-risk people by July and aim to reach herd immunity levels by November.

On Wednesday, officials conducted a vaccination preparedness drill at the Incheon international airport, west of Seoul, mobilising special freezers and running through scenarios such as a terror attack, theft and transport faults.

"We need to accomplish our tasks in the actual process of transport, storage and distribution without any errors," Moon said during the drill.

"Repetitive exercises are important to ensure there won't be any trials and errors that have occurred overseas, including missing vaccines and cold chain problems."

Vans carried containers specially made by Korean Air , the nation's largest airline, for the Pfizer and Moderna vaccines, which require ultra cold storage.

One container can carry up to 60,000 doses at temperatures of minus 18 Celsius (minus 0.4 F) for about 100 hours, an airline official said.

Vaccine centres designated in 250 indoor gyms and community halls nationwide have been fitted with cold storage equipment.

South Korea reported 467 new COVID-19 cases by Tuesday, as numbers rebounded above 400 in recent days, boosted by continuing cluster infections.

Health authorities said four of this month's 27 locally transmitted cases were caused by the more transmissible variants. That takes to 39 the total infections by British and South African variants in South Korea.

Authorities have extended by two weeks a requirement to observe social distancing, urging vigilance ahead of next week's Lunar New Year holidays, when tens of millions of Koreans usually travel across the country.

If the situation improves, however, the government might ease some measures this weekend, including a restaurant curfew, health ministry official Yoon Tae-ho told a briefing.

(Interactive graphic tracking global spread of coronavirus: https://graphics.reuters.com/world-coronavirus-tracker-and-maps/)

(Reporting by Hyonhee Shin; Additional reporting by Sangmi Cha; Editing by Clarence Fernandez and Kim Coghill)