Turkish authorities lifted a curfew imposed to fight Kurdish militants in an area of southeast Turkey's largest city, Diyarbakir, on Monday but security was tight as Kurds celebrated the Newroz spring festival.

NATO-member Turkey is on heightened alert after a series of bombings which have killed more than 80 people, most recently a suicide bombing in Istanbul that killed three Israelis and an Iranian on Saturday.

Turkey's interior minister said a Turkish member of the Islamic State militant group (IS) was responsible for that bombing. Kurdish militants have also carried out bomb attacks.

The Baglar district governor's office in Diyarbakir said the six-day-old curfew in the Kaynartepe neighbourhood was being lifted from 6 a.m. (0400 GMT). It had been declared after moves by Kurdistan Workers Party (PKK) militants to set up barricades, dig ditches and plant explosives there, but the statement said security force operations had achieved their goal.

Violence has surged in the mainly Kurdish southeast since a 2-1/2 year ceasefire with the PKK collapsed in July. The militants have focused their strikes on security forces in southeastern towns, triggering a series of curfews.

Security sources said security measures in Diyarbakir were raised to their highest level ahead of the Newroz celebrations, which at the height of the PKK insurgency in the 1990s were marked by clashes between protesters and security forces.

Security sources said hundreds of police were involved in operations to stop and search vehicles at various points around Diyarbakir overnight and carried out identity checks on guests at hotels and cafes in the area.