The incident took place late Friday evening when Almqvist, 29, and his girlfriend decided to visit a nightclub in the Stureplan district of Stockholm following a crayfish party, the Aftonbladet newspaper reported.
But when Almqvist attempted to gain entry to the club's VIP-room, bouncers blocked his way, resulting in a confrontation which the bouncers claim turned violent.
According to a report filed with police, Almqvist pushed one of the guards and then punched the guard in the face.
The sitting member of Sweden's parliament, the Riksdag, then allegedly dealt out several blows to the bouncer before being taken away by agents from Swedish security service Säpo.
In an interview with the Svenska Dagbladet (SvD) newspaper, head of marketing for Stureplansgruppen, the company that operates the nightclub, said that Almqvist behaved “extremely aggressively”.
“We think its extremely unsettling that he became so violent that the Swedish Security Service was forced to remove him from the area,” Johan Rydervärn told the newspaper.
Police who were called to the scene placed Almqvist under arrest and took him in for questioning.
He was also ordered to leave a urine sample before being released later on Saturday morning.
In a statement on the Sweden Democrats' website, Almqvist disputes the bouncers' version of events, claiming that he was the one who was attacked.
According to Almqvist, two bouncers “jumped” him when he asked why it was taking so long to gain entry into the club's VIP-area.
“There was no verbal altercation and not the least big of violence from our side,” he wrote.
Speaking with Aftonbladet, Almqvist said he plans on reporting the bouncers to police for attacking him and for giving false statements.
“They accused me of doing something I didn't do. That's a serious crime,” he told the newspaper.
In addition, Almqvist has filed a libel complaint against Stureplangruppen's Rydervärn, according to the Dagens Media newspaper.
“Firstly, he caused me great harm when he went out an lied to the media. Secondly, this is a way to make sure he doesn't dare to continue lying,” Almqvist told Dagens Media.
Speaking with SvD on Monday, Sweden Democrat spokesperson Martin Kinnunen emphasised that Almqvist still had the support of the party.
"We have total confidence in him. We know him well and think that his account is credible," he told the newspaper.
Almqvist, who was born in Stockholm but was elected to the Riksdag as a representative of Västra Götaland County in western Sweden, served as the head of the Sweden Democrats' youth wing until shortly after gaining a seat in parliament following the 2010 elections.
In parliament he sits on the Social Insurance Committee and is also a member of the Nordic Council's Swedish delegation.