Hong Kong police have been filmed arresting a pro-democracy protester with the help of a suspected undercover officer.

A video shows what appears to be a plain-clothed police officer wrestling a protester to the ground during the arrest.

In the video, the protester, whose face is bloodied, can be heard shouting “don’t do this, I beg you” as officers pin him down.

The footage was captured in Hong Kong’s Causeway Bay on Sunday, during the 10th consecutive weekend of protests sparked by an extradition bill.