Turkey has protested to the United States, after accusing American troops of arresting 11 of its soldiers in northern Iraq.
"It's a totally ugly incident, it's something that shouldn't have happened," said Prime Minister Recep Tayyip Erdogan.
Several hours later, Mr Erdogan said some of the men had been released but did not specify the number.
Reports in the Turkish newspaper Hurriyet suggested the special forces troops were detained in the city of Sulaymaniyah on Friday on suspicion of planning an attack on a regional governor.
Around 100 American soldiers are said to have stormed the barracks being used by the Turkish troops, arresting 11 soldiers and six civilians and taking them to the regional capital of Kirkuk.
In response, Turkey on Saturday closed Habur border gate, the only crossing point for aid and goods between Turkey and Iraq.
The private Turkish NTV television station said Turkish military officials had discussed other possible retaliatory measures if the troops were not released.
These included closing Turkish airspace to US military flights, stopping the use of the southern Incirlik air base and sending more troops into northern Iraq.
A State Department spokeswoman in Washington said Secretary of State Colin Powell had discussed the detentions with Turkish Foreign Minister Abdullah Gul, the Associated Press reported.
Turkey keeps a wary eye on developments across its border
For decades, Washington regarded Ankara as a firm friend, but the war in Iraq created unprecedented tension between them.
Relations soured when Turkey refused to allow US forces to be stationed on its territory in the run-up to the conflict in Iraq.
The BBC's Ankara correspondent, Jonny Dymond, says northern Iraq is still perceived by Turkey as part of its sphere of influence.
Ankara has long feared the creation of an independent Kurdish state in northern Iraq which could encourage separatist aspirations among its own Kurdish population.
Since the end of the war, most Iraqi Kurdish leaders have stuck to the line that they are seeking autonomy rather than outright independence.
But several thousand Turkish troops have remained within northern Iraq, ostensibly to keep track of the movements of Turkish Kurdish guerrillas who waged a separatist campaign in the 1980s and 1990s.
But the Turkish presence is resented by the Kurds who run the area.