Turkish and international human rights organisations have called on Turkey to end what they term an "orchestrated campaign of intimidation and judicial harassment of civil society", after prosecutors moved to indict 16 prominent activists.

Turkish state media have reported that prosecutors are seeking life prison terms without parole against philanthropist businessman Osman Kavala and 15 other people they accuse of "attempting to overthrow the government" for supporting mass anti-government protests in 2013.

Nine human rights organisations, including Amnesty International, gathered in Istanbul on Wednesday and called the accusations "absurd"

They said Turkey is obliged to protect human rights defenders under international law.

The 2013 protests started with an environmental cause - protecting Gezi Park in central Istanbul.

They quickly broadened into demonstrations opposing the government.