Swiss authorities stopped an Islamic preacher at the German border late on Friday to prevent him speaking at a rally against Switzerland's ban on building minarets.
The Federal Migration Office had already said that the presence of Pierre Vogel at Saturday afternoon’s rally in the capital Bern was considered a danger for public law and order.
Vogel, a former boxer who converted to Islam in 2001, tried to cross into Switzerland by car near Basel at about 10:30pm but was refused entry and forced to return to Germany.
The group organising the protest, the Central Council of Muslims, is protesting a ban on the construction of new minarets, which Switzerland voted for two weeks ago in a referendum.
Vogel, known for his conservative positions, said he wanted to encourage Muslims in Switzerland to come out of their social isolation and help reduce mistrust.
The main Muslim organisations in Switzerland had not been invited to the public protest and do not support it.
Muslims make up about 4.5 per cent of the Swiss population. Most of them are moderate Sunnis, notably immigrants from the former Yugoslavia and Turkey.
A previous demonstration in Bern in 2006 was attended by about 1,000 people.
swissinfo.ch and agencies