By Noel Randewich and Armando Tovar
MEXICO CITY (Reuters) - A deadly swine flu never seen before has broken out in Mexico, killing at least 16 people and raising fears of a possible pandemic.
The World Health Organisation said it was concerned at what it called 800 "influenza-like" cases in Mexico, and also about a confirmed outbreak of a new strain of swine flu in the United States.
Mexico cancelled classes for millions of children in its sprawling capital city and surrounding area on Friday after authorities noticed a higher number of flu-like deaths than normal in recent weeks.
"It is a virus that mutated from pigs and then at some point was transmitted to humans," Health Minister Jose Angel Cordova told the Televisa network.
He put the death toll at 16 confirmed cases and dozens of other suspected deaths. WHO said about 60 people have died in the country.
The Geneva-based U.N. agency said it was in daily contact with U.S., Canadian and Mexican authorities and had activated its Strategic Health Operations Centre (SHOC) -- its command and control centre for acute public health events.
U.S. health officials said on Thursday that seven people had been diagnosed with a new and unusual H1N1 swine flu virus, different from seasonal flu, but all had recovered.
(Additional reporting by Maggie Fox in Washington and Stephanie Nebehay in Geneva; Writing by Frances Kerry, Editing by Kieran Murray)
