KABUL - The NATO-led International Security Assistance Force (ISAF) announced on Monday that it will initiate probe into the alleged killing of civilians in an operation in Afghanistan's Nangarhar province, according to a statement released by the military alliance.

"The International Security Assistance Force is investigating an operation conducted in Nangarhar province yesterday that resulted in Afghan civilians being accidentally killed and wounded, "the statement said.

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Coalition forces observed three insurgents emplacing an improvised explosive device along a road After gaining positive identification, coalition forces engaged the enemy.

Following the engagement, coalition forces observed three vehicles travelling to a local hospital. The passengers of the vehicles later reported the roof of their compound collapsed during the engagement, resulting in the casualties.

"This is a deeply regrettable accident," said US Army Col. Patrick Hynes, ISAF Joint Command Combined Joint Operations Center director.

"We are investigating this tragic incident to find out how it happened to try and prevent it from happening again. We will meet with local leaders in the area and ensure they understand what happened. Our thoughts and concerns are with the families."

Earlier in the day, some media outlets quoting provincial officials reported that a couple and their four children were killed overnight when a NATO air strike mistakenly hit their home in Khogyani district in the province some 120 km east of capital Kabul.

A joint investigation team consisting from representative of ISAF, Afghan Ministry of Defense and Interior Ministry left for neighboring Kunar province Monday morning to probe into alleged killing of scores of civilians caused by military forces.

According to Kunar's provincial governor, Afghan and foreign forces during operations had left 65 people dead including civilians and anti-government militant over the past four days in the province.