A "medical emergency" involving lead singer Chad Kroeger has forced Nickelback to cancel the second leg of its North American tour.

Kroeger has been diagnosed with "an operable cyst on his voice box," the Canadian band said on its official website Tuesday.

Kroeger said he was sorry the band had to scrap dates for its No Fixed Address tour.

"I am definitely not thrilled with the prospect of being silent for many weeks to come when I could be out there playing for our fans," he said in a statement.

"I am relying on my doctor and his team to help get my voice back in good form as quickly as possible."

The cancellation comes after the band nixed a number of shows over the weekend. Anyone holding tickets will be refunded.

Nickelback guitarist Ryan Peake and bassist Mike Kroeger issued a video explaining the situation.

"We completely understand people will be upset about this," said Peake, "but we need him to properly take care of his voice so that we can continue to do this."

Chad Kroeger is due to undergo surgery in three weeks, followed by a period of doctor-ordered rest.

The 40-year-old, Alberta-born musician, who is married to Canadian pop rocker Avril Lavigne, is expected to make a full recovery. Kroeger confirmed that his wife was recovering from a severe case of Lyme disease earlier this year.

Nickelback hopes to resume the tour in Europe in Finland on Sept. 30, and return to North America sometime in 2016.