Turkish security sources say hundreds of Turkish troops in an armored column crossed into northern Iraq late Monday heading toward a Kurdish militant camp.

The sources say hundreds of Kurdistan Workers Party fighters are believed to be based in Iraq's Haftanin valley, about 20 kilometers from the Habur border post near the city of Zakho. Turkish warplanes took off earlier from bases in Diyarbakir and Malatya to launch airstrikes on the camp.

The Firat News Agency, which supports the Kurdish cause and the PKK, confirmed Monday that Turkish troops had entered northern Iraq.

Their incursion is the latest phase of a cross-border operation that began following last week's attack by PKK fighters that killed 24 Turkish soldiers along the Iraqi border, the army's biggest losses since 1993.

On Saturday, the Turkish military said it had killed 49 militants during two days of fighting in a valley on the Turkish side of the frontier.

Ankara's swift reaction has fueled speculation that Turkey could move to a full-blown incursion to clear out PKK camps deeper inside northern Iraq.