* Some of heaviest fighting for years
* At least 50 militants killed in past week, sources say
* At least 10 Turkish troops per month have died this year
By Seyhmus Cakan
DIYARBAKIR, Turkey, Sept 10 (Reuters) - Turkey's armed forces have killed more than 50 suspected Kurdish militants in two separate operations over the past week, security sources said on Monday, one of them involving air strikes over the border in northern Iraq.
The military said in a statement that Turkish jets hit 14 targets in northern Iraq between Sept. 5-9 and that 25 militants were "rendered ineffective" by the operation, a term it uses to refer to rebels being killed, wounded or captured.
The strikes were part of a large ground-and-air offensive against fighters from the separatist Kurdish Workers Party (PKK) in southeastern Turkey last week, involving 2,000 troops as well as F-16 fighter jets and attack helicopters.
Security sources said last week Turkish warplanes had struck targets inside Iraq and that 26 PKK fighters had been killed on Turkey's side of the border alone since the start of the operation, which focused on Sirnak province bordering Iraq and Syria.
On Monday, security sources said Turkish troops had killed a further 26 PKK militants in a separate operation over the weekend in Turkey's southeastern Hakkari province.
It is was not immediately possible to independently verify the death toll.
This summer has been one of the bloodiest in Turkey since the PKK, which is considered a terrorist organisation by Turkey, the United States and the European Union, took up arms against the state in 1984 with the aim of carving out a Kurdish state.
More than 40,000 people have been killed in the nearly three-decade-old conflict.
The Turkish military said it had killed 330 PKK militants inside Turkey between February and August and that 88 Turkish soldiers had been killed between the start of the year and the end of last week, at least 10 troop deaths per month.
One soldier was killed by an improvised explosive device in Sirnak province on Sunday, while two soldiers were killed and seven wounded during the clashes in neighbouring Hakkari, security sources said.
Turkey has stepped up air operations on suspected PKK rebels in northern Iraq over the past year after an increase in PKK attacks, and the raids have fuelled tension between Ankara and the Kurdistan Regional Government (KRG).
Ankara has linked the surge in violence to the unrest in neighbouring Syria and Prime Minister Tayyip Erdogan has accused Syria's President Bashar al-Assad of arming the PKK militants.
Turkey has raised the possibility of military intervention in Syria if the PKK were to launch attacks from Syrian soil. On Wednesday, the military conducted a major military exercise on the Syrian border, a clear warning to Damascus.