A leading Kurdish lawyer appears to have been targeted for execution during a gun battle between unknown attackers and police in the Turkish city of Diyarbakir. Witnesses said the city's Bar Association President Tahir Elci was shot in the head.

Elci, who had been criticised in Turkey for saying the banned Kurdistan Workers Party (PKK) was not a terrorist organisation, was talking to media near a mosque when gunshots rang out.

"The moment the statement ended, the crowd was sprayed with bullets," a local official from the pro-Kurdish HDP party, Omer Tastan, told Reuters. "A single bullet struck Elci in the head."

A policeman was also killed, Turkish President Tayyip Erdoğan said in a speech shortly after the incident.

In video footage shot by the Dogan News Agency, men hiding behind the minaret of a nearby mosque started firing at Elci and people standing with him.

"A person ran towards Tahir Elci, fired with one hand and then started to run away," Dogan reporter Felat Bozarslan told Reuters. "Then fighting started."

Three officers and an unknown number of journalists were wounded in the clashes, witnesses told the Agence France Presse, news agency.

Elci was arrested in October for alleged "terrorist propaganda" following a TV interview in which he said the PKK was not a terrorist organisation but had been released pending trial. He faced seven years behind bars if convicted. An outspoken critic of state policy towards the minority Kurdish population, Elci described the group as "an armed political movement with political demands".

Turkey, the US and the European Union all classify the PKK, which demands greater autonomy for Turkey's Kurds, as a terrorist organisation.

Elci had also criticised some of the tactics implemented by the PKK which has killed dozens of Turkish soldiers since a two-year old ceasefire between the government and the militants collapsed in July.

Diyarbakir, the largest city in Turkey's troubled, mainly Kurdish south-east has been hit by some the worst violence in years after the hostilities resumed.