The trial began in an Istanbul court and the suspects include 46 lawyers, three law firm employees and one journalist, the Anatolia news agency said.

They are accused of links with the Union of Kurdistan Communities (KCK), an organisation deemed by the authorities as the urban wing of the outlawed Kurdistan Workers' Party (PKK), Anatolia said.

Prosecutors accuse the defendants of liaising between the PKK and the organisation's imprisoned leader Abdullah Ocalan.

The suspects "have intentionally undertaken a mission of setting the organisation's (PKK) strategy ... and ordering its members for action," the indictment said.

Seven suspects each face up to 22.5 years in prison on charges of "forming and running an armed organisation".

The remainder face up to 15 year sentences on charges of "membership in an armed organisation".

International rights and lawyers' groups have expressed "concern" in a joint declaration Friday over the trial, also noting that similar cases were ongoing or pending against other key Kurdish or pro-Kurdish civil society actors.

The wider crackdown against the outlawed Kurdish rebels and their supporters began in 2009.

Since then, 700 people have been arrested pending trial over alleged links to the KCK, according to government figures, although critics say the true number arrested tops 3,500.

Ankara says the KCK wants to replace Turkish government institutions in the Kurdish majority southeastern Anatolia with its own political structures.

The PKK, listed as a terrorist organisation by Turkey and much of the international community, took up arms in the Kurdish-majority southeast Turkey in 1984, sparking a conflict that has claimed some 45,000 lives.