DIYARBAKIR, Turkey - Turkish soldiers and Kurdish militants clashed on Tuesday in the most intense battles of the separatist conflict this year, with 26 combatants killed in fighting at three army outposts in the southeast, officials and security sources said. Up to 100 fighters from the Kurdistan Workers Party (PKK) launched simultaneous dawn attacks on three military observation points in Hakkari province near Turkey's mountainous border with Iraq, killing eight soldiers and wounding 19, the sources said. In subsequent clashes, Turkish troops killed 18 PKK fighters, the prime minister's office said.

The attacks come at a time when Turkey is making new efforts to address the grievances of the Kurdish minority to end a conflict that has scarred the region for three decades.

"We have never regarded terrorism as a matter of negotiation with anybody, and we will never do so. The only thing to do is for terrorists to lay down their arms," Prime Minister Tayyip Erdogan told reporters in Mexico, where he is attending a G20 Summit.

"We will continue our struggle until the end, and sooner or later, we will succeed in our fight against terror," he added.

President Abdullah Gul condemned the violence. "I curse this treacherous attack," he said in a statement. "The terrorist group wants to sabotage the atmosphere of trust and stability and is continuing its inhumane bloody attacks."

The head of Turkey's pro-Kurdish Peace and Democracy Party (BDP), whose members are frequently accused of ties to the rebels, made a striking call for the PKK to halt hostilities.

"The PKK should stop all kinds of armed activity. The government should also halt (military) operations. Let them give a political solution a chance," BDP Chairman Selahattin Demirtas told a meeting of the party's parliamentary group.

"This war must end. The deaths must stop. We can't stand by and watch the youngsters kill each other," he said.

The PKK fighters used rocket launchers and rifles at the start of the attacks and operations were continuing against the militants, the sources said. The militants were believed to have crossed the border from nearby northern Iraq.