Four people were killed in clashes between security forces and Kurdish militants on Tuesday, security sources said, as fighting widened in southeast Turkey following a suicide bombing that killed 37 people in the capital Ankara.
Kurdistan Workers Party (PKK) fighters blocked roads and halted vehicles in the Kaynartepe neighborhood of the city of Diyarbakir and clashed with security forces sporadically through the night as a police helicopter flew overhead, witnesses said.
No one has claimed responsibility for Sunday's car bomb that tore through a crowded transport hub in Ankara, but security officials have said it involved two militants, one of them female, from the outlawed Kurdistan Workers Party (PKK).
Violence has surged in mainly Kurdish southeast Turkey since a 2-1/2 year PKK ceasefire collapsed in July. The militants have focused their strikes on security forces in southeastern towns, some of which have been under curfew.
One police officer and three militants were killed in the fighting in the Baglar district of the southeastern city of Diyarbakir, the security sources said.
A curfew was imposed in Baglar's Kaynartepe neighborhood from 3 a.m. (0100 GMT) after moves by militants to set up barricades, dig ditches and plant explosives, authorities said.
The curfew was later widened to encompass more city streets as clashes continued in the morning. Gunfire and explosions rang out across the city and police in armored vehicles parked on street corners called for people to stay inside.
Conflict in Diyarbakir, the southeast's largest city, has until now has been focused in the Sur district, parts of which have been devastated by the fighting.
Read also: Turkey bombed Kurdish rebels in Iraq after Ankara suicide car-bombing
Following the Ankara bombing, the Turkish military launched air strikes on Monday and struck northern Iraq's Qandil mountain area where the PKK's main bases are. The military said 45 PKK militants were believed to have been killed.
The strikes by F-16 and F-4 jets destroyed two weapons depots and two Katyusha rocket positions, the military said in a statement.
The conflict has also fueled political tensions, with President Tayyip Erdogan repeatedly calling for lawmakers from the pro-Kurdish Peoples' Democratic Party (HDP) to face prosecution, accusing them of being an extension of the PKK.
The PKK, which says it is fighting for autonomy for Kurds, is designated a terrorist group by Turkey, the United States and the European Union.
Speaking on Monday evening, Erdogan said the definition of terrorist needed to be broadened to include supporters.
"It may be the terrorist who detonates bombs and pulls the trigger, but it is these supporters who enable them to achieve their goals," he said in a speech.
"Being an MP, an academic, journalist, writer or civil society group executive does not change the reality of that person being a terrorist," he said.