Around 100 guerrillas from the outlawed Kurdistan Workers Party (PKK) besieged four state and security installations simultaneously in the town of Beytussebap at 10pm local time on Sunday.

At least seven members of the security services were wounded in fighting around the town in Sirnak province, and clashes were continuing in nearby mountains, the sources said.

They said the bodies of three PKK fighters who had been killed in the battles were brought to a local morgue.

Fighting between the army and the PKK has intensified in recent months, a development which some Turkish officials and analysts have linked to the chaos in neighbouring Syria.

The militants have also kidnapped growing numbers of Turkish officials. Security sources said the PKK had seized a local leader of Prime Minister Tayyip Erdogan's ruling AK Party in the southeastern province of Hakkari.

More than 40,000 people have been killed in the conflict between the PKK and Turkish forces since the militants launched their insurgency 28 years ago with the aim of carving out a separate state in the mainly Kurdish southeast.

The PKK is listed as a terrorist organisation by Turkey, the United States and the European Union. Turkish officials have said the group is getting direct support from Syria's President Bashar al Assad and Kurdish groups in Syria.

Mr Assad, who is battling a 17-month-old bloody uprising against his rule, has denied that Syria had allowed the PKK to operate on Syrian territory.

Since June last year, nearly 800 people have died in the conflict in Turkey, the International Crisis Group estimates.