This image is from a video of a fight posted on YouTube. (YouTube)

Police have a warning for teenage street fighters in Dartmouth: You're responsible for every punch.

A group called the Northbrook Fight Club is arranging bouts between fighters and inviting friends to watch.

One fight posted on YouTube shows two high school-aged boys brawling in the snow in T-shirts, their noses and mouths covered in blood. They're wearing gloves with UFC — Ultimate Fighting Championship — on the knuckles.

Stewart Briggs discovered the fight club on Saturday when he looked out his back window near Northbrook Park in Dartmouth and saw a group of youths gathered in a circle.

"All of a sudden I saw something happen that didn't seem right," Briggs told CBC News.

Joseph Benoit, a Grade 10 student at Dartmouth High School, said he turned down an invitation to fight last month.

"I think it's the student's decision if they want to get involved in a dangerous situation. If they don't, then they decline. If they want to then it's their own stupidity and they'll accept," he said.

Benoit said the club has been around since the summer. Police, however, are only hearing about it now.

Const. Brian Palmeter, spokesman for Halifax Regional Police, said fighting is dangerous business even if two people consent.

"People don't realize that when they throw a punch, they're responsible for the end outcome. So whether the person falls and hits their head as a result of that, they're responsible," said Palmeter.

Palmeter said police are investigating. He suggests that parents look for videos online to see if their children are members of the fight club.