Geneva police had to break up fights outside a polling station set up for Brazilians on Sunday.
Some supporters of the two candidates came to blows.
Although there were no arrests, witnesses say the atmosphere was tense.
The result from the Geneva poll showed the race was virtually neck and neck.
The contender, Lula da Silva beat the incumbent Jair Bolsonaro by just 52 votes out of a total of nearly 4,000 cast.
Bank details compromised
British digital bank Revolut has admitted handing customer information to fraudsters who impersonated a European government agency
Watch theft victim speaks out
A luxury watch dealer just across the French border from Geneva has broken his silence about a violent robbery earlier this month
Crans Montana hearings due before end of year
Jessica Moretti, who ran the Constellation bar in Crans-Montana, is now living in near-isolation in the Valais village of Lens more than eight months after the deadly New Year's Eve fire
Better news for economy
Switzerland's economy will grow 1.7% this year — nearly double the 0.9% expansion forecast in June, the State Secretariat for Economic Affairs said yesterday
Geneva budget plan unveiled
Geneva has now put figures to its austerity plan — a CHF 546 million deficit for 2027, even after CHF 247 million in cuts
Summer fires increase
Firefighters across French-speaking Switzerland tackled far more vegetation fires this summer than in any of the past five years
