The 17-year-old victims suffered serious injuries after being attacked on Lambton View, Harehills, at about 3.45pm on Monday – at around the same time as the carnival procession was making its way along nearby Roundhay Road.
Detectives arrested two males, aged 17 and 18, yesterday on suspicion of wounding with intent.
They have been released on bail pending further enquiries.
Police are continuing to appeal for information in relation to the incident.
Anyone with information should contact Leeds CID via 101 or Crimestoppers, anonymously, on 0800 555111.