The secular military dislikes the Islamist-rooted ruling AK Party and political analysts say the generals are trying to portray it as weak on terrorism.
AKP, which denies any Islamist agenda, is widely expected to win re-election in July.
Buyukanit stressed the need to act within the law in tackling the security threat. Turkey's parliament, now in recess ahead of the July 22 elections, would have to reconvene to authorise any serious cross-border military operation.
"We have to conduct our fight on a legal basis. We cannot go beyond the laws," he said in Isparta, southwest Turkey.
Tayyip Erdogan, the prime minister, said last week that Ankara would take military action if necessary.
More than 30,000 people have been killed in fighting between security forces and rebels of the outlawed Kurdistan Workers Party (PKK) since the group launched its armed campaign for an ethnic homeland in southeast Turkey in 1984.
Casualties have risen in recent months as PKK fighters hiding in northern Iraq cross the mountainous border into Turkey to attack security and civilian targets.
Buyukanit repeated his accusation that PKK rebels were receiving support from some foreign countries, including nominal allies of Nato-member Turkey.
He did not name these countries, but Ankara has criticised the United States for failing to crack down on the PKK in Iraq.
Turkey has also accused some European countries including Belgium and Denmark of providing help to the separatists.
Buyukanit said there were many "collaborators" in Turkish towns and villages providing support to the PKK, which is considered a terrorist organisation by Turkey, the EU and the United States.
But he also said that the problem of Kurdish separatism could not be solved by purely military means.
Citing economic and social factors, he said: "Terrorism is multi-dimensional. Apart from the armed struggle, it has to be combated in other ways too."
Turkey's mainly Kurdish southeast region is dogged by poverty, high unemployment, poor education and low investment. The armed conflict has hampered the region's economic progress.