Police in the U.K. have launched an investigation after two men were stabbed at the Wireless Festival in London on Sunday night (14Jul13).

The victims were knifed by an unknown attacker during a headline set by Justin Timberlake and Jay Z, and they were taken to hospital for treatment.

One of the men, who is in his 20s, was in a critical condition as Wenn went to press. The other victim, also in his 20s, was in a stable condition.

Police are appealing for witnesses to the attack.