Turkish fighter jets have bombed dozens of Kurdish separatist targets in northern Iraq, local television has reported.
Some 20 warplanes hit around 50 positions of the Kurdistan Workers' Party (PKK), in the ZAP-Khakurk region on Thursday, Turkish broadcaster NTV said.
The army has not yet confirmed the raid and there was no immediate news of casualties.
Anita Mcnaught, Al Jazeera's correspondent in the Turkish capital Ankara, said: "We understand that the Turkish armed forces were made aware of the movements of a significant number of rebels and decided to launch the strikes to pre-empt their arrival in Turkey.
"What is known about these sorts of attacks is that since the end of 2007 they have been made with the assistance with the US military, as part of a deal at the end of President Bush's [of the US] adminsitration."
Experts believe that the US shares military intelligence with Turkey about PKK movements.
The PKK, which is seeking autonomy for Kurds living in southeast Turkey, has led an armed struggle against the Turkish government for more than two decades.
About 40,000 people have died in the conflict since it began 25 years ago.
Turkish troops have previosuly entered northern Iraq at the end of 2007 and stepped up intermittant air stikes against PKK fighters based in northern Iraq since then.
Mcnaught said: "This is one of the biggest strikes in the last two years.
"This was a very much larger strike than usual - almost 50 locations. And a day long attack involving all these fighter jets.
"It is hard to ascertain the damage given the difficult territory."
Kurdish groups have been able to benefit from instability in Iraq to find safehaven in northern Iraq from where they could launch attacks in Turkey.