Two soldiers were killed in Bingol, southeast Turkey, in an operation involving 7,000 to 8,000 soldiers. Further south in the provinces of Sirnak and Hakkari, which border Iraq, at least 15,000 soldiers were fighting the PKK, the sources said.
Turkey has stepped up operations against PKK inside Turkey and, since the end of a February land offensive against militants based in northern Iraq, has launched a series of air strikes against PKK targets in the neighbouring country.
Sunday's deaths add to a toll of eight security personnel killed in the southeast in the last week alone, according to information from the General Staff.
On Friday night and early Saturday Turkey's armed forces launched their second air operation on northern Iraq in a week, the biggest round of air strikes this year, according to military sources.
The armed forces tend to step up operations in the spring when the snow melts, making it easier to move around the mountainous region.
In February, the army conducted a eight-day land offensive into northern Iraq, which prompted concern in Washington about further regional instability and was watched closely on financial markets.
Like the United States and the European Union, it considers the group a terrorist organisation.
Last Mod: 27 Nisan 2008, 13:02