SIRNAK, Turkey — Dozens of military vehicles headed toward the Iraq border and protesters demanded tough action against Kurdish rebels today after 12 soldiers were killed Sunday in an ambush. The attack has pushed Turkey closer to a possible incursion into Iraq to target insurgents hiding there.

An AP Television News cameraman saw a convoy of 50 military vehicles, loaded with soldiers and weapons, heading from the southeastern town of Sirnak toward Uludere, closer to the border with Iraq.

It was unclear whether the vehicles were being sent to reinforce troops engaged in fighting with rebels on Turkish soil, or were preparing for possible cross-border action. Tens of thousands of Turkish troops are already deployed in the border area.

The pro-Kurdish Firat news agency, based in Belgium, released seven names that it said were those of Turkish soldiers allegedly abducted by separatist fighters in the ambush Sunday. It said an eighth soldier was also captive but did not release his name. Turkey's private NTV television has reported eight soldiers missing, but the government has not confirmed the report.

The guerrilla ambush that killed a dozen soldiers on Sunday outraged an already frustrated public, with nationalists staging demonstrations and opposition leaders calling for an immediate strike against rebel bases in Iraq, despite appeals for restraint from Iraq, the U.S. and European leaders.

About 2,000 protesters in Istanbul, mostly members of an opposition party, denounced the attack and urged the government of Prime Minister Recep Tayyip Erdogan to resign, the private Dogan news agency reported.

Protesters also gathered in Ankara, the capital, and the Mediterranean port city of Mersin. Some 13,000 school children in Bilecik in eastern Turkey held a minute of silence while people marched down a main street, waving the Turkish flag, the state-run Anatolia news agency reported.

In Bursa, in northwest Turkey, protesters walked to a military conscript office and asked to enlist to fight rebels.

Turkey's military said Sunday it had launched an offensive backed by helicopter gunships in retaliation for the attack, shelling rebel positions along the rugged Turkish-Iraqi border. It said 32 rebels had been killed in the offensive so far.

The military convoy included trucks carrying containers full of weapons, around a dozen artillery guns and some 150 soldiers.