Turkish authorities on Sunday said Yuksekova, near the border with Iran, and Nusaybin, on the border with Syria, would be under an open-ended 24-hour curfew.

Security forces have for months been carrying out controversial military operations in urban centers in the largely Kurdish populated southeast in a bid to flush out Kurdistan Workers' Party (PKK) fighters who have set up barricades, trenches and booby traps.

Military operations in several cities have been accompanied by weeks-long curfews that amount to a siege on the civilian population.

Rights groups and the pro-Kurdish Peoples' Democratic Party (HDP) say the operations have displaced tens of thousands of people and killed scores of civilians, including women and children.

Large parts of Cizre were destroyed in weeks of military operations.

The government says it has killed hundreds of "terrorists" in an attempt to restore order, but has remained relatively quiet on the number of security forces killed and civilian losses.

The operations have laid waste to several Kurdish towns, making them look like war-torn Syria.

As the curfews in Nusaybin and Yuksekova were to go into effect authorities eased a curfew in parts of Diyarbakir, the largest Kurdish city in the region, where the historic Sur district has become an urban wasteland after three months of fighting.

The curfew announcement for Nusaybin and Yuksekova led some citizens to flee the towns, Turkish media reported. The curfews will prevent anybody from entering or leaving the cities. Similar curfews in other towns have left civilians trapped for weeks without supplies.

In Nusaybin, Turkish media published images of tanks parked in a school in anticipation of military operations.

Since a two-year ceasefire between the PKK and Turkish state broke down last summer the country has been wracked by some of the most destructive fighting since the height of the conflict in the early 1990s.

At least 40,000 people have been killed in nearly three decades of fighting between Turkey and the PKK, who are fighting for greater autonomy and Kurdish rights.