SIRNAK, Turkey — Dozens of Turkish military vehicles streamed toward the Iraqi border with heavy artillery and ammunition Monday after Kurdish guerrillas killed a dozen soldiers and claimed to have captured eight in an intensifying crisis threatening to spill into Iraq.

Arab nations joined the United States and Europe in urging Turkey's government not to attack suspected guerrilla bases in the Kurdish region of northern Iraq, while Turkish citizens rallied across the country demanding action against the rebels.

Iraq's president claimed the guerrillas would announce a cease-fire. But the rebels denied that, saying a cease-fire they declared in June was still in place.

With tensions worsening, the Turkish foreign minister said his government was pursuing a diplomatic solution to halt rebel operations out of havens in Iraq but warned that it wanted to see results soon if an escalation in military action was to be avoided.

An Associated Press Television News cameraman saw a convoy of 50 Turkish army vehicles, loaded with soldiers and weapons, including 155-mm howitzers, heading from the southeastern town of Sirnak toward Uludere, closer to the border.

Trucks towing artillery pieces covered with camouflage tarpaulins were trailed by khaki-colored trucks that appeared to be loaded with ammunition. Armored personnel carriers with helmeted Turkish soldiers manning heavy machine guns escorted the trucks.

It was unclear if the vehicles were joining troops fighting with rebels on Turkish soil or were preparing for a possible cross-border offensive, which was authorized by Turkey's parliament last week.

At least five U.S.-made transport helicopters ferrying soldiers and Cobra helicopter gunships also were seen flying toward the frontier.

The Pentagon has said 60,000 Turkish soldiers have deployed along the border. The north is one of the few relatively calm Iraqi regions, and the United States fears an incursion by its ally Turkey could worsen the Iraq war.

After weeks of stepped-up clashes between Turkish troops and rebels, tensions racheted even higher after a guerrilla ambush Sunday killed 12 soldiers and left eight missing. The army said 34 rebels died in a counterattack.

The rebel Kurdistan Workers' Party said its fighters captured the missing soldiers — a claim that would make it the largest seizure since 1995, when guerrillas grabbed eight soldiers, took them to northern Iraq and held them for two years before letting them go.

"Right now, these soldiers are hostages in the hands of our forces," a senior PKK commander, Bahoz Erdal, was quoted as telling the pro-Kurdish Firat News Agency in Belgium. "Their health condition is good. One of them was slightly injured, but was being taken care of by our medics."