Turkish activists who helped launch mass anti-government protests last year will go on trial on Thursday in what critics have said is a further attempt to crush dissenting voices.

Turkish activists who helped launch mass anti-government protests last year will go on trial on Thursday in what critics have said is a further attempt to crush dissenting voices.

Twenty-six alleged leaders of Taksim Solidarity, an umbrella group of civil society, union and political groups, face up to 29 years in prison for their part in the demonstrations that marked the biggest challenge yet to the 11-year rule of Prime Minister Recep Tayyip Erdogan.

The charges include founding a crime syndicate, violating public order and organizing illegal protests through social media.

Last June's protests started as a small environmentalist movement to stop the re-development of Istanbul's Gezi Park and quickly blew up into wider nationwide demonstrations against Erdogan's authoritarian style.

Those going on trial on Thursday include doctors, architects and engineers who led the protests that left at least eight people dead and some 8,000 injured after police brutally cracked down on protesters.

The activist group was formed in 2012 after the government announced plans to redevelop Gezi Park, one of the last remaining green spaces in central Istanbul, and neighboring Taksim Square, the country's most symbolic rallying point.

The group met Erdogan at the height of the unrest to discuss the protesters' demands, only to be accused by the premier of being "traitors" aiming to destabilize the government.