Turkish Cobra helicopters pounded Kurdish rebel positions near the Iraqi border on Tuesday and Prime Minister Tayyip Erdogan reaffirmed Ankara's readiness to send troops over the frontier despite U.S. opposition.
Witnesses in Sirnak province saw plumes of smoke rising from the mountains after the helicopters flew over rebel positions.
Earlier, a convoy of up to 40 army vehicles headed east towards the border in brilliant sunshine. Troops scoured the hillsides for landmines, a favored weapon of the guerrillas.
Three Turkish soldiers have been killed in the past 24 hours in the border area. A fourth died on Monday in Tunceli province hundreds of km (miles) to the north in a landmine explosion.
Turkey has massed up to 100,000 troops, backed by tanks, artillery, warplanes and combat helicopters along the Iraqi border in preparation for a possible cross-border incursion into northern Iraq where some 3,000 rebels are believed to be hiding.
The Sabah newspaper said some 250 rebels of the outlawed Kurdistan Workers Party (PKK) were trying to escape Turkish security forces in the border area. The figure could not be independently confirmed.
"Turkey has to take military action against terrorism. Our security forces are continuing their operations without interruption," Erdogan told members of his ruling centre-right AK Party in parliament in Ankara.
"We are at the stage of making a decision and we will make the decision on our own... We are employing all our resources to get results in the shortest time."
The United States and Iraq have urged Turkey to avoid a major military incursion, fearing this would destabilize the wider region. Washington and Baghdad have shown no appetite for tackling the PKK despite repeated appeals from Ankara.
Iraqi Kurdish leader Masoud Barzani told Tuesday's Milliyet newspaper he wanted the PKK to lay down its weapons but he also criticized Turkey for refusing to speak about the issue with his autonomous Kurdish administration in northern Iraq.
Ankara insists on speaking only with the central government in Baghdad and suspects Barzani of planning an independent Kurdish state in northern Iraq. It fears this could stoke separatism among Turkey's own large ethnic Kurdish population.
Turkey witnessed a huge outpouring of support for its military in celebrations on Monday marking the 84th anniversary of the founding of the modern republic. With nationalist feelings at fever pitch, Erdogan has appealed for calm.
"Reactions on the street (to PKK attacks) must not be directed towards our Kurdish citizens," Erdogan said, referring to a spate of minor attacks on individuals and Kurdish-owned businesses in Turkey.
Turkey is home to more than 12 million Kurds. Erdogan's government has eased some restrictions on Kurdish culture and language but Kurdish activists say it needs to do much more.
Ankara blames the PKK for the deaths of more than 30,000 people since the group launched its armed campaign for an ethnic homeland in southeast Turkey in 1984. The United States and the European Union, like Turkey, brand the PKK as a terrorist group.
U.S., Turkish and Iraqi officials will make fresh diplomatic efforts to stave off a major military operation when they attend a conference of Iraq's neighbors in Istanbul this weekend.
Erdogan will then travel to Washington for talks on the issue with U.S. President George W. Bush next Monday.
Erdogan said on Tuesday he would tell Bush Turkey expected "urgent, concrete steps" from the United States against the PKK. He would also seek an explanation of why PKK rebels are using U.S.-made weapons in their fight with Turkish forces.