Dressed in a black belted leather jacket and tight black trousers, the star began singing acapella under a spotlight. The stage then lit up as the women walked in from the wings to join her as the beat kicked in, with the crowd cheering as they realized what was happening.
As her guests remained still and silent, the Swedish-Gambian performer, 25, who is one of the Nordic nation's most successful music exports in recent years, belted out the lyrics to her 2015 track 'Easy'. The words include "Shoulder to shoulder, I know it could be easy, yeah" and "What would the world be, if we let it be just fine".
She then segued into her international hit 'Hard Times', receiving a standing ovation as she wrapped up her appearance, which was shown live on Swedish public service broadcaster SVT.
Swedes rushed to social media to compare Sey's move to Beyonce's apparent political statement at the US Superbowl halftime show earlier this month, when she emerged flanked by black female back-up dancers dressed in the style of the civil rights group the Black Panthers while her own jacket appeared to echo one of Michael Jackson's famous outfits from the 1990s.
However the Swede said she wanted people to make up their own minds about her motives.
"I started with my closest friends, and then they were allowed to bring as many others with them as there was space for on the stage," she told Swedish newspaper Dagens Nyheter.
"The whole thing that I was up there trying to convey is that people should use common sense to think and interpret things themselves."
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She said that she was not trying to promote a "trend to talk about black people's rights in society", explaining that she was rather "inspired by the injustices in the world".
"On the other hand. I do everything Beyonce tells me to do," the singer added, with a laugh.
Sey's statement comes as immigration and integration remain among the most debated issues in Sweden, after the country took in record numbers of refugees in 2015, but then decided to re-introduce border checks after local authorities said they were struggling to manage the influx.