The funerals turned into seas of red and white as crowds of mourners marched waving the national flag. They shouted slogans against the separatist Kurdistan Workers' Party (PKK), whose militants ambushed a military unit near the Iraqi border Sunday.

The bloody attack left Prime Minister Recep Tayyip Erdogan's government under immense pressure to order a military operation into northern Iraq, where the PKK has bases.

"The martyrs are immortal, the motherland is indivisible," roared the crowd in the town of Keskin, about 100 kilometres (60 miles) southeast of Ankara, where one of the slain soldiers was buried.

"Hang Apo," demonstrators chanted, as a procession of about 7,000 people, about a fifth of the town's population, marched behind the casket. Apo is the nickname of jailed PKK leader Abdullah Ocalan.

Government and military officials attended the funeral ceremonies, held in 11 provinces across the country and broadcast live on several national television stations.

The German ambassador to Turkey, Eckhart Cuntz, attended a funeral in the central city of Eskisehir, reports said.

In Bursa, in the northwest, traffic was paralysed in the city centre as the demonstrators thronged the main boulevard. They brandished huge Turkish flags and portraits of soldiers killed by the PKK in its 23-year campaign for Kurdish self-rule in the southeast.

"We are all soldiers, we will smash the PKK," mourners chanted in the yard of the ancient Ulu mosque, where prayers were held for another soldier.

Elsewhere, protestors called on Erdogan to order the army to northern Iraq and denounced Iraqi Kurdish leaders, whom Ankara accuses of tolerating and even supporting the PKK in their autonomous region in northern Iraq.

"Treacherous Talabani... give us the dogs," read a pancard brandished at a funeral in Afyon, central Turkey, addressing Iraqi President Jalal Talabani.

Talabani, himself a Kurd, has said that Baghdad is unable to capture and hand over PKK rebels based in northern Iraq as Ankara requests.

Thousands of people also demonstrated in cities other than those where the 12 funerals were held.

"Down with the PKK, down with the USA," chanted demonstrators in Istanbul, venting their anger on Washington, for its perceived failure to help end the PKK safe haven in Iraq.

Sunday's bloodshed at the Iraqi border followed the killing earlier this month of 15 soldiers in two days, and an attack on a van in which 13 people were shot dead. Both attacks have been blamed on the PKK.

With Turks holding daily street demonstrations since Sunday, sales of Turkish flags were booming, with one company reporting a 200-percent increase.

Several offices of Turkey's main Kurdish political movement, the Democratic Society Party, have been stoned and vandalised and political leaders have strongly warned against any reprisals targetting the Kurdish community.