Sum 41 frontman Deryck Whibley, seen in front signing autographs with bandmate Jason McCaslin in Toronto in 2007, requires time off for rehabilitation for his back injury, the band said. ((J.P. Moczulski/Reuters))

Sum 41 is bowing out of its remaining dates on the Warped Tour this month, as frontman Deryck Whibley continues to recover from injuries recently sustained in Japan.

The Canadian pop-punk band, which got its start in Ajax, Ont., announced on its website this week it will pull out of Warped Tour performances through Aug. 15. The decision affects dates in California, Idaho, Washington and Oregon.

"Being a part of the Warped Tour this summer meant a lot to us," not having toured for two years, drummer Steve Jocz said in a statement.

"We were excited to be back in front of our fans and are very disappointed that we have to pull off the tour. We know that it would be more frustrating for the fans if we can't give it our all. Deryck is doing everything he can to get himself better and we're there for him."   

Last week, the band took a break from the music and extreme sports tour — which played dates in the U.S. and Canada this summer — to travel to the Summer Sonic Festival in Tokyo and Osaka, Japan.

However, while at a bar in Japan, Whibley was attacked by three individuals and later hospitalized. He was diagnosed with a slipped (or herniated) disc and, despite doctors' recommendations that he rest, the singer and guitarist proceeded with Sum 41's Japanese gigs.

According to the band statement, Whibley's condition "has not improved" and the cancellations were required for him to begin rehabilitation for the injury, from which he is expected to make a full recovery.

The band also vowed it will be back on the road by the end of the month for upcoming fall concert dates abroad, including stops in Switzerland, France, Belgium, Italy, Germany, Russia, the U.K., the Netherlands and the Czech Republic.