Venting on their Facebook page, Marie Fredriksson and Per Gessle updated on Saturday night: "Just spent 90 minutes at one of the world's worst airports, Johannesburg. Could actually be the No1 on that scary list ... Good God, how about some organisation with customs etc?"

Within two hours of the posting, 255 Facebook users liked the comment and more than 50 South Africans subscribed to the page agreed. Some described the airport as a "horror", blaming the government for not improving service delivery.

Their comments were met with anger by other South Africans and international fans, who said a 90-minute wait was "not so long". They described standing in long queues at British and US airports.

The duo, who performed last week in Johannesburg, Durban and Cape Town as part of their world tour, stepped into the debate: "We love South Africa. You know that! But someone should fix the logistix at Joburg Airport."

Airports Company of SA's spokesman at OR Tambo, Unathi Batyashe-Fillis, said security surveillance footage showed that there were long queues at the emigration checkpoint when Roxette were leaving.

But, he said the airport had not established why.

"Emigration [and immigration] services are provided by the Department of Home Affairs and, though Airports Company SA provides the infrastructure, we are not able to answer questions regarding problems at emigration," she said.

Batyashe-Fillis said the airport's customer-care division was not told of Roxette's departure and ground staff, appointed to assist celebrities, were not on hand.

"OR Tambo International Airport, as the hub airport of South Africa, receives a substantial number of high-profile individuals."

She said that, since the 2009 launch of the Airport Management Centre, on-time departure performance had improved from 76% to 88%.

"The airport's overall departure punctuality yesterday [Saturday] was above 86%."

Long queues and delayed departures were thrust into the international spotlight last month when the head of the UK Border Force, Brian Moore, had to explain to British MPs why queues at Heathrow International Airport's passport control section were so long.

The airport service quality passenger surveys by Airports Council International showed that OR Tambo International's score rose from a satisfactory rating of 3.6 in 2008 to an excellent 4 last year.