An investigation into a number of South African airlines has been launched over alleged price-fixing during this year’s FIFA World Cup.

The country’s Competition Commission said that it was investigating domestic operators for “allegedly colluding” over ticket costs and pricing strategies during the tournament in June and July.

Companies under investigation include South African Airways, 1time, SA Airlink, Mango and SA Express, as well as Comair, which is part owned by British Airways.

Internal flights will be relied on heavily by football fans during the tournament due to the large distances between the host cities and the lack of overland public transport.

Organisers are laying on extra flights during the World Cup, with many airports remaining open all night. There will be an estimated 1,800 daily domestic flights.

However a number of South Africans have complained of excessive price increases, prompting the investigation by the Competition Commission.

Deputy competition commissioner Thembinkosi Bonakele said that a company, which he declined to name, had submitted a proposal to fix prices.

“There is an issue about whether other airlines actually followed that proposal or they didn’t,” Bonakele told Johannesburg’s 702 Talk Radio. “The proposal was very clear about the strategy that needed to be followed around the World Cup period.”

The commission said it would refer the case to the competition tribunal for a hearing and request a penalty if the airlines were found guilty. Passengers could then be allowed to seek compensation.

South African Airways told The Guardian: “SAA undertook to fully co-operate with the commission in exchange for leniency from prosecution under the Competition Act. SAA can further confirm that discussions with the commission relating to the application are under way and that the airline has the full intention of complying with the legislation.”

Other companies denied any involvement in price-fixing.

Comair chief executive Gidon Novick said: “There has been no discussion of pricing. We set our own pricing, which is set in the context of the market. Airlines watch what other airlines are doing, but we certainly don’t collude.”

South Africa hotels have also been accused of increasing prices to five times the usual rate for holidaymakers in June.