Planes chartered by the United States to transport terror suspects across Europe made stops in Sweden as late as 2006, the Svenska Dagbladet (SvD) newspaper reports.

When the Swedish government requested information clarifying the purpose of the flights, a minor diplomatic crisis erupted and stopovers in Sweden by US government chartered planes carrying prisoners from the war on terror stopped soon thereafter.

Secret US diplomatic cables published by WikiLeaks reveal that two planes carrying terror suspects landed at Stockholm’s Arlanda airport in 2006, one in February and one in April.

According to SvD, the cables are the first public confirmation that both flights had prisoners on board.

The United States’ chargé d’affaires in Stockholm at the time, Stephen V. Noble, wrote in a cable to Washington that the government of Sweden, led at the time by Social Democratic prime minister Göran Persson, had concerns over reports that planes flown by the United States’ CIA intelligence service had been landing at airports throughout Europe.

According to the cable, the Swedish government was bothered by the fact that the plane which had landed in February had been registered as a private plane when in fact it had been chartered by the US government.

Noble describes how, a few days ahead of the scheduled landing of a US plane in April, a high ranking US diplomat was called to the Swedish foreign ministry and made to answer a series of questions about the CIA plane and its mission.

The Persson-government made it clear that it wanted to know if the United States was transporting prisoners and indicated that future flights would be given closer scrutiny.

Confirmation that the planes were transporting prisoners came in April 2006 after a daring “surveillance operation” was ordered by Swedish security service Säpo and carried out without the knowledge of the Americans.

On Säpo’s orders, Swedish military intelligence agents dressed up as airport service personnel and boarded the plane. The agents reported back that the plane was carrying prisoners.

In April 2009, the Expressen newspaper first reported that Swedish intelligence agents had spied on a CIA plane at Arlanda and found it filled with chained prisoners clad with black hoods and unable to move.

A spokesperson for Säpo confirmed for SvD that the agency had carried out a surveillance operation at Arlanda airport in April 2006 on a US government plane suspected of carrying terror suspects, but refused to elaborate on what the operation revealed.

Based on the evidence reviewed by SvD, no more secret American prisoner transports have landed in Sweden since 2006.