DIYARBAKIR, Turkey (Reuters) - Kurdish militants killed five members of Turkish security forces in three separate bomb attacks on Tuesday near the Syrian and Iranian borders, the army and security sources said, in an intensification of conflict in southeast Turkey.

Hundreds of security forces personnel, militants and civilians have been killed since a 2-1/2 year ceasefire between the Kurdistan Workers Party (PKK) and the state collapsed in July.

One soldier was killed and six more wounded in a bomb attack early on Tuesday in Nusaybin near the Syrian border, the army said. The area has been under a curfew since March 14 when security forces launched operations against militants there.

Two police officers and one soldier were killed and nine security force members were wounded in a PKK bomb attack on a military vehicle in the town of Yuksekova, near the Iranian border, security sources said.

A third roadside explosive device planted by the militants below up an armored vehicle in the Mazidagi district of Mardin province, also near Syria, killing one police officer and wounding three others, the sources said.

Separately, the military said 23 Kurdish militants were killed in clashes in Nusaybin, Yuksekova and Sirnak on Monday.

The PKK, designated a terrorist organization by Turkey, the United States and European Union, is carrying out a violent struggle for autonomy in the mainly Kurdish southeast. More than 40,000 people have been killed in the conflict since it began in 1984.