Hundreds of mourners follow a vehicle transporting the coffin of Tahir Elci during his funeral in Diyarbakir on Sunday.

AFP/Diyarbakir

Tens of thousands of people on Sunday mourned the killing of a prominent Kurdish human rights lawyer in Turkey's troubled southeast that has raised new tensions with its biggest ethnic minority.

Tahir Elci, one of the country's best-known advocates for Kurdish rights, was killed on Saturday during a gun battle between police and unidentified gunmen in southeastern city of Diyarbakir while making a statement calling for calm. Two police were also killed.

The death of Elci, who was the head of Diyarbakir Bar Association, triggered protests from Diyarbakir to Istanbul, where police used water cannons and tear gas to disperse the demonstrators.

Some 50,000 people mourned as his casket draped in the red, yellow and green Kurdish flag and red carnations made its way through the streets of Diyarbakir - the biggest city in the mainly Kurdish southeast, an AFP correspondent reported.

Many colleagues including Metin Feyzioglu, head of the Turkish Bar Association, carried his coffin, while prayers and slogans echoed from the crowd, who had gathered behind a huge black banner that read: "We will never forget you."

"Martyrs do not die, Tahir Elci is immortal," demonstrators chanted in Kurdish.

Elci was killed by a single bullet to his head, but it was not clear whether the attack directly targeted the lawyer or whether he died in the crossfire during shooting between the assailants and police.

"We are very sad. It's a bullet that targeted peace and orphaned an entire people. We owe him a lot because this person struggled for peace. All he wanted was peace," said Diyarbakir resident Kadri Kavut, 47.

"One Tahir was lost but 1,000 other Tahirs will replace him," said Mehmet Tekin, another mourner.

'Political murder'

Turkey's southeast has been hit by the worst violence in years after a two-year ceasefire between the Turkish government and the outlawed Kurdistan Workers' Party (PKK) - considered a terrorist organisation by Turkey, the US and the European Union, collapsed in July.

Elci's killing has triggered new tensions, with his supporters accusing the state of being behind the murder.

The lawyer had caused controversy by saying in an interview the PKK was not a "terrorist" organisation.

He was arrested then released in October pending trial and risked up to seven years in prison if convicted on charges of "justifying terrorism". But Elci had also been critical of the PKK.

Addressing the crowd at the funeral, pro-Kurdish People's Democratic Party (HDP) leader Selahattin Demirtas said he doubted the "political murder" would ever be resolved, like similar killings in the past.

"So many similar losses have taken place on our lands in the past. But we were never able to bid farewell with our minds at rest, wondering if those responsible will ever be caught."

Several rights groups, including Human Rights Watch (HRW) and the International Federation for Human Rights (FIDH), urged an independent investigation and demanded the perpetrators be brought to justice.

"The murder of Tahir Elci is a devastating blow not only to human rights activists but to all who want to see justice and rule of law prevail in Turkey," said Emma Sinclair-Webb, senior researcher at HRW.

Prime Minister Ahmet Davutoglu said on Sunday that the gun found next to Elci's body had also been used in the attack on the policemen and belonged to the "terrorists," in an apparent accusation that the PKK was behind the crime.

CCTV footage released on Saturday showed Elci hiding behind a man holding a gun as the shooting starts.

Plain-clothed police are seen shooting at two men running towards Elci, but a moment later the lawyer is seen lying face down on the ground, with a pistol next to his body.

A hugely prominent figure in legal circles in southeast Turkey, Elci had defended three reporters for the US-based news organisation Vice News after they were detained in Diyarbakir in August.

Two British reporters were released but their Iraqi colleague Mohammed Ismael Rasool is still in detention. Vice News said Elci had remained the lead lawyer on the case.