Turkey's pro-Kurdish opposition was critical of the UN for holding Monday the first World Humanitarian Summit in Istanbul, charging that President Recep Tayyip Erdogan was violating human rights and igniting "sectarian" violence in Syria.
"We remain deeply concerned about the possibility that hosting such a critical meeting might serve the Erdogan regime to cover up the gross rights violations and crimes that it has been committing," the Peoples' Democratic Party (HDP) said in a letter to UN Secretary General Ban Ki-moon.
Erdogan, who has been moving recently to consolidate his grip on power, regularly accuses the HDP of being a wing of the banned Kurdistan Workers' Party (PKK), though the group denies these charges.
Since the peace process between the state and the PKK fell apart last year amid mutual recriminations, many hundreds of people have died in renewed violence and half a million from the mostly Kurdish south-east are estimated to have fled their homes.
Last week, the Turkish parliament, dominated by Erdogan's Islamic-rooted Justice and Development Party (AKP) voted to strip the immunity of 50 of the HDP's 59 legislators, in a move that drew concern from the European Union and United States.
Western allies of NATO-member Turkey have also been worried by crackdowns on the media and government critics.
The HDP, which says there is a rise of "totalitarianism" in Turkey, expressed upset with Europe for not pressing harder on the issue of the country's Kurdish minority, while making a deal with Ankara on stemming migration flows.
"The EU has agreed to keep silent in the face of systematic human rights violations against the Kurdish civilians in return for Erdogan regime’s cooperation to take under control the onward movement of refugees that the regime itself has unleashed," the HDP said, calling the government a "rogue force" in the region.
Turkey currently hosts well over 2 million refugees from Syria. The government says the border remains open to those who need to flee the civil war in the neighbouring state, but human rights groups dispute this, saying it is effectively closed.