Turkey's military says one of its helicopters has crashed into a house on the outskirts of the Afghan capital, killing 12 Turkish soldiers on board and at least four people on the ground.

Authorities say the Sikorsky helicopter was on a mission as part of the NATO force in Afghanistan when it crashed Friday in the Bagrami district of Kabul province.

Turkish Foreign Minister Ahmet Davutoglu said the aircraft went down while trying to make an emergency landing. He told reporters, “it is a grave accident, our grief is deep.”

Afghan officials said two children were killed when the helicopter hit the house. Two other civilians also died.

NATO said the cause of the crash is being investigated and that initial reporting indicates there was no enemy activity in the area at the time. The NATO commander, General John Allen, expressed his deepest sympathies to the families of the Turkish troops and the Afghan civilians who died.

It was the deadliest coalition helicopter crash in Afghanistan since last August, when a Chinook helicopter was apparently shot down by militants in Wardak province, killing 30 Americans.

Both United Nations Secretary-General Ban Ki-moon and U.S. State Department spokeswoman Victoria Nuland said they were deeply saddened by the news of the helicopter crash and conveyed their condolences to the Turkish and Afghan governments.

Turkey has some 1,800 troops in Afghanistan as part of the NATO force. Turkey's mission is limited to patrols and its troops do not take part in combat operations.

In eastern Afghanistan, NATO says one of its service members died Thursday in a bomb blast.