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By Gareth Jones

ANKARA, June 27 (Reuters) - The head of Turkey's powerful armed forces reaffirmed on Wednesday his view that a cross-border operation into northern Iraq was needed to crush Kurdish rebels based there.

His comments pile more pressure on Turkey's government to allow a military operation, just weeks before parliamentary polls in which security and terrorism issues will loom large.

The staunchly secular military dislikes the Islamist-rooted ruling AK Party and political analysts say the generals are trying to portray it as weak on terrorism. AK, which denies any Islamist agenda, is widely expected to win re-election in July.

"I have said (in April) that we need a cross-border operation and that this would bring benefits. I repeat this view now," General Yasar Buyukanit told a news conference shown live on Turkish television.

But he 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.

Prime Minister Tayyip Erdogan told Reuters 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 sharply in recent months as PKK fighters hiding in northern Iraq cross the mountainous border into Turkey to attack security and civilian targets.

HELPING MILITANTS

The head of Turkey's land forces, General Ilker Basbug, told the news conference there were between 2,800 and 3,100 PKK rebels based in northern Iraq.

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 militants.

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 added that the problem of Kurdish separatism could not be solved by purely military means.

"Terrorism is multi-dimensional. Apart from the armed struggle, it has to be combated in other ways too," he said, citing economic and social factors.

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.

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