Belarus' top security agency, the KGB, has summoned a Swedish advertising team for questioning after the group air-dropped hundreds of parachute-wearing teddy bears that carried pro-human rights messages onto the soil of the authoritarian former Soviet state.
The summons, signed by an investigator named P Tsernavsky and posted on the KGB's website on Saturday, said the agency was investigating the "criminal case" of the advertising group's "illegal crossing" into Belarusian airspace.
The agency threatened the Swedes with fines or "correctional work for up to two years, or imprisonment for up to six months" if they did not show up in 10 days.
The KGB said it wants the Swedes to participate in its "investigative actions" so it can clarify the role each person played and help it decide how to deal with two Belarusian men accused of aiding them.
The July 4 teddy bear drop by Studio Total infuriated Belarus' President Alexander Lukashenko, who fired two generals over it.
Earlier this month, Belarus effectively expelled Sweden's ambassador and ordered the Nordic state to close its embassy over the incident.
The Swedes reciprocated by barring entry to the new Belarusian ambassador to Stockholm and asking two junior Belarusian diplomats to leave the country.
Although the teddy bear drop was not officially cited as a reason for the embassy closure or the barring of Sweden's envoy, Lukashenko was cited on Thursday as accusing Swedish diplomats of involvement in the stunt.
One of the Belarusian accused of aiding the Swedes, a journalism student, was arrested after he posted photos of the teddy bears on his personal website.
The other Belarusian is a property agent who is said to have offered the Swedes an apartment when they visited Belarus some time before the stunt.
Tomas Mazetti, Studio Total's co-founder who piloted the plane in the teddy bear drop, said he received the summons via email, and that it demands that he and two colleagues, Hannah Frey and Per Cromwell, appear.
Mazetti said the letter did not spell out why the Swedes were being summoned, but his understanding was that they had been asked to appear as witnesses - not suspects.
"The letter refers to 'refusal or avoidance of a victim or a witness to appear', it doesn't refer to suspects," he said.
Mazetti said the Swedes would seek guarantees from the KGB before travelling to Minsk.
"We're going to demand guarantees that the KGB does not indict us. They've said they would agree to that previously, but we want guarantees," he said.
The KGB statement pledged to observe the Swedes' rights "in accordance with the Belarus' legislation".
"We have nothing against helping them in their investigation to clarify just how we did it," Mazetti said.
He said political experts have warned that Lukashenko may be using the two Belarusians as pawns to force the Swedes to go to Minsk. "It's pure blackmail," he said.
Studio Total has previously staged attention-grabbing campaigns by burning up stacks of cash and setting up a fake sex-school in Austria.
Mazetti said it orchestrated the non-commercial air-drop of the 879 teddy bears to shine a light on Belarus' poor record on human rights and freedom of speech and to embarrass its military, a pillar of Lukashenko's power.
Lukashenko has ruled Belarus, a nation of 10 million people, since 1994, repressing opposition groups and independent news media while preserving a quasi-Soviet economy with about 80 per cent of industry in state hands.
He has earned the nickname in the West of "Europe's last dictator".