Thailand is facing bans on new international flights and increased inspections after the International Civil Aviation Organization flagged significant concerns about the country's aviation safety, officials said Friday.

The ICAO's designation of Thailand as a "significant safety concern" has not been announced publicly by the U.N. agency but governments were informed last week. Kwak Young-pil, an official from South Korea's Ministry of Land, Infrastructure and Transport, said Friday that the ICAO made the designation on March 20.

Japan has blocked new flights from Thailand following the ICAO decision and South Korea is considering similar measures, officials said. Existing flights aren't affected.

Among the airlines forced to cancel flights are budget carriers Thai AirAsia X, NokScoot and Asia Atlantic Airline, Thailand's Department of Civil Aviation said in a statement. Flag carrier Thai Airways is also affected.

The disruptions come ahead of Thailand's traditional new year, known as Songkran, a heavy travel season when airlines typically increase the number of flights. Thailand is one of the world's top tourist destinations and its tourism industry is crucial to the economy, employing millions of people.

Thai Airways President Jarumporn Chotikasathein said the airline would have to cancel "about five" charter flights that were being planned for the April holiday schedule. He said Thai Airways and other Thai carriers will also have to undergo increased inspections by regulators from other countries as a result of the ICAO designation.

Thailand was audited by the ICAO in January, about a decade after its last assessment in 2005. Audits assess a country's overall ability to ensure aviation safety. Among the areas considered are personnel licensing and training, airworthiness assessment and certification, accident investigation and airline operations oversight, according to a report by Watson Farley and Williams, an international law firm with a commercial transport practice.

The ICAO office in Bangkok referred questions to its headquarters in Montreal, which could not immediately be reached for comment.

The Thai ministry's statement did not give details on the ICAO's concerns or recommendations but said that it planned to inform countries about the status of its safety standards and "the solutions to fix the faults that were found in the inspection as soon as possible."

Japan's Civil Aviation Bureau informed Thailand's civil aviation department by email earlier this week that it will not allow new charter flights operated by Thai-registered carriers to fly into Japanese airports.

The Japanese ban covers any "change of aviation services" and also bars airlines from changing the type of aircraft normally used on scheduled routes, the Thai civil aviation department said.

In Tokyo, a spokesman the bureau, Noriaki Umezawa, said the measure was a temporary one issued because of concerns the airlines may not fully meet international safety standards.

South Korean said it was considering a similar ban.

Kwak, the South Korean transport official, said it was highly unlikely that new flights would be approved. NokScoot was planning to start flights to Seoul's Incheon Airport in May.

He said flights currently operating between Thailand and South Korea will not be affected.