A US military helicopter crashed Sunday in Afghanistan killing five soldiers and leaving several others injured.

The helicopter crashed near Bagram air base, north of the capital. The air base houses most of the 11,600 coalition forces in Afghanistan.

The US military said the cause of the crash was as yet unknown.

The soldiers onboard the helicopter were involved in Operation Mountain Resolve, a military plan to destroy bases used by operatives linked to Osama bin Laden’s al-Qaeda terror network in the remote areas of Nuristan and Kunar.

In a separate incident, two US soldiers were wounded when their vehicle hit a land mine near Shkin, close to the border with Pakistan.

The news comes as Mullah Omar, former leader of the Taliban, called on fellow Afghans to fight back against US military in the country.