Pakistan angrily rejected a U.N. claim that it is harboring Taliban leaders, accusing multinational troops in Afghanistan of doing little to crack down on commanders of the insurgency.

NATO and the Afghan government say Taliban and Al Qaeda guerrillas are launching attacks on U.S.-led coalition forces in Afghanistan from neighboring Pakistan. Violence rose sharply in Afghanistan in 2006, with militants killing about 4,000 people in what was the deadliest year since the U.S.-led coalition swept the Taliban from power in 2001.

Chris Alexander, the deputy head of the U.N. Assistance Mission in Afghanistan, said Monday in Kabul that most of 142 Taliban leaders listed as such by the U.N. in 1999 "continue to organize, plan and carry out terrorist activities in this country and in this region."

Some of those leaders "were in Pakistan for at least a part of 2006," Alexander said, without elaborating.

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In a statement received by The Associated Press on Wednesday, Pakistan's Foreign Ministry said the accusation was "unsubstantiated" and demonstrates "ignorance of ground realities" in Afghanistan.

The ministry also accused the U.N. of "insensitivity to Pakistan's efforts to counter militancy and terrorism."

Pakistan, a close U.S. ally in the war against terrorism, has repeatedly stated it is doing all it can to prevent the Taliban militants from using Pakistan as a base. The statement, which was dated Tuesday, noted that Pakistan's efforts have led to the arrest of several leading Taliban figures.

"One may ask how many Taliban on the list have been apprehended by the Afghan and multinational forces especially when the statement (also) implies their presence inside Afghanistan," the statement said.

Late last year, Islamabad announced plans to fence and mine parts of its long and rugged frontier with Afghanistan to stop the cross-border insurgency.

The plan was criticized by Afghan and U.N. officials who said it would not stop the insurgency, but only hinder cross-border travel by ethnic groups living on both sides of the border.

"Those who criticize Pakistan's decision should offer viable alternatives on controlling such activity," the Foreign Ministry statement said.

U.N. "officials would be well-advised to restrict themselves to their mandate and refrain from questioning the intentions and sincerity of Pakistan, which has done more than any other country in the international efforts against terrorism," the statement said.

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