Iraq's president, a Kurd, ordered Kurdish guerrillas Sunday to lay down their arms or leave Iraq after the rebels ambushed a military unit near Turkey's border, killing 12 soldiers and increasing pressure on the Turkish government to stage a cross-border incursion.

Hours after the ambush, Turkey fired about 15 artillery shells toward Kurdish villages in the border area in northern Iraq but caused no casualties, an Iraqi army officer said.

Iraqi President Jalal Talabani urged the separatist Kurdistan Workers' Party, or PKK, to stop their attacks amid fears an incursion would destabilize the relatively peaceful autonomous Kurdish region in northern Iraq.

"We have appealed to the PKK to desist fighting and to transform themselves from military organizations into civilian and political ones. But if they (the PKK) insist on the continuation of fighting, they should leave Kurdistan, Iraq and not create problems here. And they should return to their countries and do there whatever they want," Talabani said at a joint news conference with Kurdish leader Massoud Barzani.