Military courts in Pakistan have sentenced 13 militants to death for terrorism-related offences including the 2013 massacre of 10 foreign mountaineers, the army said Tuesday.

Tehreek-e-Taliban Pakistan (TTP) member Irfan Ullah was sentenced for the attack on the base camp at Nanga Parbat, Pakistan's second highest mountain, which shocked the world and scarred the country's climbing tourism industry.

Gunmen dressed in police uniforms stormed the camp and shot dead 10 foreign mountaineers -- including one American with dual Chinese citizenship, two other Chinese, three Ukrainians, two Slovakians, one Lithuanian and one Nepalese and a Pakistani guide.

"Today Chief of Army Staff confirmed death sentences awarded to another 13 hardcore terrorists, who were involved in committing heinous offences relating to terrorism, including killing of foreign tourists at Nanga Parbat," the army said in a statement.

The other 12 had been charged with various severe crimes from attacking schools and an airport, to killing security officials, civilians and damaging helicopters.

Pakistan has hanged more than 300 people since lifting a moratorium on the death penalty in December 2014, many of them convicted in closed military courts which critics say fail to meet fair trial standards.

The nuclear-armed South Asian nation lifted the six-year moratorium and amended the constitution to allow military courts to try hardcore militants after Taliban gunmen killed more than 150 people, most of them children, at an army-run school in Peshawar on December 16, 2014.

In June 2014, the army launched an operation in a bid to wipe out militant bases in North Waziristan tribal area and end the bloody decade-long Islamist insurgency that has cost thousands of lives.

Pakistan has been battling a homegrown Islamist insurgency for more a decade following its decision to side with the US-led coalition against the Taliban in Afghanistan.