Waving Bulgarian and EU flags, several hundred Bulgarian Muslims protested in the southern town of Pazardzhik on Tuesday against the start of a trial of 13 people accused of spreading radical Islamist ideas.

Relatives and supporters of the 13 suspects say they were preaching traditional ideas, not radical Islamist propaganda.

The trial of the 13 members of the Al Waqf-Al Islami organisation started on Tuesday.

The organisation is not officially registered in the predominantly Orthodox Christian country in which about 10 per cent of the population are Muslims, according to the latest census.

The suspects are charged with preaching an anti-democratic ideology, with seeking to impose Sharia law, with leading and participating in an unregistered religious entity and with preaching religious intolerance.

According to the indictment, the belief systems of the defendants are broadly in line with elements of Salafism.

One of the defendants has a prior conviction on a similar charge for which he was handed a three-year suspended sentence with five years of probation and a public reprimand.