By Humeyra Pamuk
ISTANBUL (Reuters) - Turkish fighter jets launched their heaviest assault on Kurdish militants in northern Iraq overnight since air strikes began last week, a government official said, hours after President Tayyip Erdogan said a peace process had become impossible.
The F-16 jets hit six targets in Iraq and were scrambled from an air base in Turkey's southeastern province of Diyarbakir, the official said, speaking on condition of anonymity because of the sensitivity of the operations.
"Last night's attack was the biggest assault since the campaign began last week," he said.
Turkey began bombing PKK camps in northern Iraq last Friday in what government officials have said was a response to a series of killings of police officers and soldiers blamed on the Kurdish militant group.
On Tuesday, fighter jets also bombed PKK targets in the southeastern Turkish province of Sirnak, bordering Iraq, after an attack on a group of gendarmes.
The PKK has said the air strikes, launched virtually in parallel with Turkish strikes against Islamic State fighters in Syria, rendered the peace process meaningless. But it has stopped short of formally pulling out.
Erdogan, however, said on Tuesday that the peace process had become impossible and urged parliament to strip politicians with links to the militants of immunity from prosecution, a move aimed squarely at the pro-Kurdish opposition.
Parliament is due to discuss the military operations in Iraq and Syria, as well as Erdogan's call for the lifting of immunity, in a closed session later on Wednesday.
Erdogan initiated negotiations in 2012 to try to end a PKK insurgency, largely fought in the predominantly-Kurdish southeast, that has killed 40,000 people since 1984. A fragile ceasefire had been holding since March 2013.
Western allies have said they recognize Turkey's right to self-defense but have urged the NATO member not to allow peace efforts with the PKK to collapse.
While deeming the PKK a terrorist organization, Washington depends heavily on allied Syrian Kurdish fighters battling Islamic State in Syria.
(Editing by Nick Tattersall/Hugh Lawson)