Upwards of 1,000 Turkish troops, backed by helicopter gunships, are attacking Kurdish militants in northern Iraq.
The Turkish government says the offensive is to avenge the deaths of 24 soldiers one day earlier at the hands of fighters from the PKK — Kurdistan Workers’ Party.
It was unclear how deep into Iraq this counter-offensive could go.
Prime Minister Tayyip Erdogan confirmed an initial air and ground campaign against the PKK militants and said the theatre of operations was to be limited to specific areas; but there is speculation there could be a full-blown Turkish incursion into Iraq as happened in 2008. Then some 10,000 Turkish troops swept into northern Iraq.
That prospect adds to concern over instability in the region. US troops are due to withdraw from Iraq this year and mutual neighbour Syria is in the grip of a bloody crackdown on pro-democracy protesters.
Earlier Erdogan and President Abdullah Gul attended the funeral of one soldier brought back to Ankara.
More than 40,000 people have died since the conflict began in 1984 and Erdogan is under pressure to show decisive action, which could jeopardise efforts to reach a peaceful settlement.
Erdogan, one of the most popular politicians in the Middle East for his harsh rhetoric against Israel and his championing of Palestinian rights, said he expects full cooperation from the international community in the fight against the PKK.
The European Union, which Turkey wants to join, has pushed the Turkish government to grant more rights to the Kurds.
But EU countries have also urged Kurdish lawmakers to distance themselves from the PKK.