Hundreds of people were attending a graduation ceremony at the madrassa in a Taliban-controlled district in northeastern Afghanistan on Monday when Afghan Air Force helicopters struck, witnesses have told AFP.

"Human Rights team on ground establishing facts. All parties reminded of obligations to protect civilians from impact of armed conflict," the United Nations Assistance Mission in Afghanistan said in a brief statement.

At least 59 people, including Taliban commanders meeting at the compound in the Dashte Archi district in Kunduz province, were killed in the attack, Afghan security sources told AFP on condition of anonymity.

Most of the civilian victims were children, they said. Government officials in both Kabul and Kunduz have given conflicting figures, with some denying any civilians had been killed or that a madrassa had been hit. Afghan officials have been known to minimise civilian casualties.

"I myself counted 35 bodies," Abdul Khalil told AFP at the hospital in the provincial capital Kunduz -- more than 50 kilometres (30 miles) from the airstrike -- where health officials said 57 injured had been taken.

"I arrived at the scene right after the airstrikes -- it was like a butcher's shop. Everywhere was covered with blood, the ground was littered with body parts, heads, limbs and other parts."

A man called Yousuf, who was at the ceremony when the airstrikes happened, told AFP he saw "blood and body parts everywhere".

Afghan television showed anguished relatives standing outside the hospital yelling "shame on you".

So far the defence ministry has denied civilians were among the casualties.

"Twenty Taliban, including the commander of their Red Unit in the district, and also a key member of the Quetta Shura were killed," defence ministry spokesman Mohammad Radmanish told AFP on Monday.

The Red Unit is the insurgent group's elite unit and the Quetta Shura is its leadership council.

The same number were wounded, Radmanish added.

- Police deny madrassa hit -

Kunduz police chief General Abdul Hamid Hamidi told AFP on Tuesday that "72 of the enemy" had been killed in the airstrike.

Hamidi added that five civilians also died and another 52 were wounded but he denied a madrassa or mosque had been hit. Security forces have donated large quantities of blood to the hospital.

The Taliban on Monday confirmed the attack on the religious school but denied that any militants had been there.

The madrassa was run by Islamic scholars sympathetic to the Taliban but the facility was open to the public, a senior Taliban commander speaking from an unknown location in Pakistan told AFP on Tuesday.

He said as many as 2,000 people were at the school on Monday, including 750 students, for a graduation ceremony, but insisted there were no senior Taliban leaders present.

He estimated that 400 people had been killed and an unknown number wounded. The Taliban are known to exaggerate battlefield claims.

Several boys with their arms and legs bandaged were seen lying in beds and along the corridors of the hospital.

One of the security sources said the Taliban had started meeting at madrassas in the hope of avoiding airstrikes.

US and Afghan forces are increasing ground and air offensives against Taliban and Islamic State insurgents as they try to get the upper hand in the 16-year war.

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