(Adds comment from ministry, NATO, U.S. military)

By Robert Birsel

KABUL, April 16 (Reuters) - A suicide bomber blew himself up among policemen doing their morning exercise in the northeastern Afghan city of Kunduz on Monday killing nine and wounding 25, the Interior Ministry said.

A Taliban commander, speaking by telephone from an undisclosed location, claimed responsibility for the attack, the worst in the relatively peaceful north since U.S.-led forces overthrew the Taliban in 2001.

It was the second deadly suicide attack on police in two days.

"It happened when the police were exercising next to the governor's building. Nine police are dead and 25 injured," an Interior Ministry official said.

Kunduz is 250 km (150 miles) north of Kabul.

Taliban insurgents, fighting to oust foreign troops from Afghanistan, have launched a wave of suicide attacks in the south and east but attacks in the north are rare.

Taliban commander Hayatullah Khan claimed responsibility and said there would be more attacks. "It was a successful strike and such bombings will continue," he said.

"All of our suicide bombers are Afghans and they are present in all Afghan cities and waiting for orders."

Suicide attacks in Afghanistan, almost unheard of three years ago, surged last year to about 140 from about 20 in 2005. There have been numerous attacks this year.

"TRYING TO BRING PEACE"

On Saturday a suicide bomber killed seven policemen and a civilian in an attack on a police station in the eastern town of Khost.

"They are getting 3,500 afghanis ($70) and trying to bring peace and stability but the enemies of Afghanistan don't want peace and stability," Interior Ministry spokesman Zemarai Bashary told reporters, referring to a policeman's monthly wage.

"The enemies of Afghanistan are the puppets of foreigners," Bashary said.

He did not elaborate but Afghan officials say the Taliban are orchestrating their insurgency from sanctuaries in neighbouring Pakistan.

Violence in Afghanistan surged last year to its worst level since 2001. Attacks eased off over the winter, as it traditionally does in Afghanistan, but violence has been picking up again over recent weeks.

Separately, Afghanistan's NATO force killed several Taliban leaders in attacks, including precision air strikes, in the southern province of Helmand over recent days, the force said.

It did not identify the Taliban leaders killed in joint operations with Afghan security forces.

"Striking at the heart of the problem and removing these key leaders has paid off," Major-General Ton Van Loon, NATO's commander in the south, said in a statement.

"Removing these extremist leaders from the equation allows freedom of choice to young men who are otherwise intimidated and coerced to join the Taliban," he said.

A separate U.S.-led force said it had captured four militants in a raid in the Barmal district of Paktika province, on the Pakistani border, and another four in Helmand on Monday.

There are about 45,000 foreign troops in Afghanistan, most in the NATO-led force. (Additional reporting by Sayed Salahuddin)

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