Los Angeles, Nov 6 (IANS): Singer Michael Buble and wife Luisana Lopilato have told their friends that they are determined to remain positive after their son Noah was diagnosed with cancer.

The parents are hopeful for their three-year-old "fighter", reports usmagazine.com.

"They are really sad but hopeful," said a source close to the singer and the model, who announced on Friday via Facebook that Noah is ill.

"They immediately got him very good care and they are hoping and praying for the best. They are getting him the best doctors around. It's really heartbreaking. This was a real shock, but they are doing everything they can," the source added.

In a statement posted to his Facebook page, Buble shared that Noah had recently been diagnosed with cancer and is undergoing treatment in the US.

The Grammy winner did not disclose any further details or specify what type of cancer Noah is battling.

"They're staying positive and Noah is a fighter," said another source, adding that the couple, who tied the knot in 2011, have been "inundated with kind wishes today, and that's really helping".