Ulrika Westerlund was taken away after participating in a demonstration with Russian gay rights activists in the middle of the Red Square in Moscow.
"People had only just started waving their flags and sung a few lines before police arrived," Westerlund says to Expressen.
Westerlund says to Swedish Radio that she is not formally arrested at this point. Another Swede is held in custody along with Westerlund and both of them have had their passports taken away.
"We only wanted to support their demonstration. We sang along and waved a rainbow-coloured scarf," Westerlund tells Swedish Radio.