A Bulgarian court is to hold a new hearing Wednesday in the trial against thirteen religious leaders accused of preaching radical Islam.

The defendants face up to five years in prison in a criminal trial, which is viewed abroad as a test for the limits of religious freedom and tolerance in the country.

A translation of religious literature from Arabic to Bulgarian, done by expert Alexander Shurin, will be presented before the magistrates. The documents have been found on the defendants' computers.

At the end of 2012, the defense council requested from Shurin to translate all texts instead of only those listed by the prosecution on grounds the latter could be considered intentional selection of evidence. This forced the translator to ask for two extensions of the deadline over the huge volume of literature.

Experts have commented it would be extremely difficult to establish the level of accuracy of the translation. In addition, at the last session, the defense lawyers said the designated experts were not competent enough.

Bulgaria's Chief Mufti, Mustafa Hadzhi is yet to take the witness stand.

Deputy Chief Mufti Birali Myumyun faced the court at a hearing at the end of December, when it emerged that he featured on the list of preachers who have received money from the Islamist organization Al Waqf Islami.

He said it was difficult to identify Salafism separately from other aspects of Islam. However, the court found inconsistencies in his testimony and the accounts given in the pre-trial proceedings in 2009.

Prosecutors say the Saudi-financed activities of the imams have been spreading religious extremism and that they have used a local soccer team to indoctrinate boys.

Prosecutors allege that three of the imams were undermining the state by encouraging people to boycott parliamentary elections and spreading religious hatred.

The other 10 are implicated in working with Al Waqfal Islami, a Saudi-financed charity that built mosques, sent boys on trips to the Middle East and financed religious education in Bulgaria that prosecutors say embraced the Salafist brand of fundamentalist Islam.

The Bulgarian government closed Al Waqfal Islami in 2003, but prosecutors say the 13 accused continued its work without a license.