(Updates after second match)
By Mitch Phillips
VIENNA, June 7 (Reuters) - Portugal served notice that they will be again be among the title challengers when they turned on the style to outclass Turkey 2-0 on an entertaining first day of Euro 2008 on Saturday.
Co-hosts Switzerland, however, got off to the worst possible start in Basel when they lost 1-0 to Czech Republic in the other Group A game and lost captain Alex Frei to a knee injury that could well rule him out of the tournament.
Austria get things underway across the border on Sunday when they play Croatia in Vienna (1600 GMT) while tournament favourites Germany play Poland in Klagenfurt (1845) in the second Group B match -- the highest security risk match of the group stage.
Seven German supporters were arrested in the town late on Saturday after German and Polish fans exchanged increasingly hostile insults but heavy rain helped keep a lid on any trouble.
There were no other reports from either Austria or Switzerland of any serious trouble and the on-field action was free too of any major controversies or ugly incidents.
In Geneva, Portugal looked dangerous throughout, hit the woodwork three times and could easily have won by more as they began their campaign to go one better than four years ago when they were runners-up to Greece on home soil.
After weathering a bright Turkish start Portugal, soon took control and Cristiano Ronaldo was denied a goal when Volkan Demirel brilliantly tipped his low free kick on to a post.
In the second half, Nuno Gomes hit a post with a shot and looped a header against the bar but in between those efforts the striker played a lovely return pass to Pepe, marauding from the back, whose deflected shot left Volkan helpless.
Substitute Raul Meireles added the second in injury time after another neat passing move.
"We wanted a bit of breathing space, a bit of leeway, and that's what we got today," said Portugal coach Luiz Felipe Scolari.
Portugal face the Czechs in what already looks like the Group A decider next Wednesday, though Switzerland, who have now failed to win any of their seven European Championship matches over three tournaments, will be wondering how they got nothing.
It had been all smiles in Basel before the match as the fans were entertained by a traditionally kitsch opening ceremony, featuring giant model cows and mass yodelling.
Once the football got underway Switzerland had the best of the chances, a penalty claim turned down and hit the woodwork.
The Czechs had hardly threatened until substitute Vaclav Sverkos, who made his international debut only last week, cleverly steered a shot beyond Diego Benaglio after 70 minutes.
Czech coach Karel Brueckner accepted that his team had been lucky while frustrated Swiss boss Koebi Kuhn said: "I told my team they can leave this stadium with their heads held high."
The defeat was compounded by the injury suffered by Frei, Switzerland's all-time leading goalscorer, who left the pitch in tears at the end of the first half with an ice pack strapped to his knee, obviously fearing his tournament was over.
Two other players who will be watching from the sidelines are Portugal goalkeeper Quim and Russia striker Pavel Pogrebnyak, who were both ruled out of the tournament with injuries on Saturday.
(Editing by Jon Bramley)