Swiss President Micheline Calmy-Rey has condemned the violence that erupted when extremists attacked a pre-election rally by the rightwing Swiss People's Party.
Critics accused police of failing to stop the militants while others pointed out that the party of the controversial justice minister, Christoph Blocher, had been stoking tensions with its hardline policies.
"I'm saddened by the images of violence," Calmy-Rey said. "A few hundred extremists can't endanger our democracy," she told the SonntagsBlick newspaper.
Calmy-Rey said militants must not be allowed to prevent people from exercising their right to free speech.
She appealed to all sides to stop playing on voters' fears in a bid to gain political advantage for the parliamentary elections later this month.
In a similar vein Interior Minister Pascal Couchepin pointed out that he had warned the members of the People's Party in the cabinet about the risk of violence in Saturday's demonstration.
"They sow the wind and reap the whirlwind," Couchepin told public television, referring to increasing tensions in the run-up to the parliamentary elections.
For his part Blocher claimed he was surprised by the escalation. His party colleague, Defense Minister Samuel Schmid, did not take part in the march.
The People's Party campaign has used controversial posters targeting foreign criminals. It has also launched a proposal to outlaw minarets and accused rival parties of plotting against Blocher.
At least 20 people were injured and dozens detained for questioning after extremists went on a rampage in the capital, Bern, on Saturday.
Riot police clashed with masked protestors in the streets of the tourist district of Bern. They prevented an estimated 10,000 People's Party supporters from marching to the parliament building.
About 100 Neo-Nazis joined the march, according to police.
The infrastructure for the planned rally was destroyed by leftwing militants.
The People's Party said the incidents were a disgrace for Switzerland. It blamed the local police and centre-left and Green politicians for failing to protect the rally.
Leftwing groups staged a separate demonstration in Bern on the same day which was not authorised by the local authorities.
However, experts say the People's Party is likely to benefit most from the incidents.
"The party says it is a victim. The leftwing militants did it a favour," said Georg Lutz, a political scientist at Bern University.
Latest opinion polls suggest the People's Party will take about 27 per cent of the vote in the forthcoming elections. It would thus remain the strongest group of the four governing parties.
The party has gained popularity in the past 15 years with its anti-European stance and its uncompromising policy on foreigners.
swissinfo with agencies
The rightwing Swiss People's Party is the largest group in parliament and one of four governing parties.
Latest opinion polls say it will maintain its share of the vote – about 27% - nearly 5% ahead of the centre-left Social Democrats.
Parliamentary elections are scheduled for October 21; cabinet will be elected on December 12.