Kaiser was admitted to the hospital due to an assault. He also posted a photo of his bruised face on Instagram.

The attack took place in front of Kaiser's Cologne home, with three unidentified men attacking him after he had gone out for a cigarette.

Kaiser made headlines around the world after proposing to his boyfriend as part of local football club FC Cologne's Diversity Day, which took place during the club's Bundesliga?game against Wolfsburg.

After his proposal went viral, a local Cologne bar accused Kaiser of fraud while he had worked there, accusations he denied.

Now, his lawyer Moritz Lange claimed the bar had made the 27-year-old's address known. The bar itself denies the accusations.

According to Lange, Kaiser received many threats since his proposal went viral. The German referee?informed police of the threats, which then sent a police presence to patrol around Kaiser's home.

"On Saturday evening, as (Kaiser) went for a walk, he received a message: 'We see you and follow you. Just wait until the police are no longer there'," lawyer Lange told German media. Not long after the message was received, Lange said, the three men appeared and attacked Kaiser.

Police said the motives for the attack remain unclear, with Germany's security services being aware of the case and looking into possible homophobic background.

Edited by: Dmytro Hubenko