At least 26 security personnel on board a military helicopter were killed on Friday in northwestern Pakistan when it went down due to technical fault, security officials said.

The crash took place on the border of the semi-autonomous Orakzai and Khyber tribal regions.

"An MI-17 (military) helicopter crashed due to a technical fault this afternoon at the border of Orakzai and Khyber agency. Twenty-six security personnel on board embraced shahadat (martyrdom)," a senior security official said.

He said that the site of crash was 20 kilometres (12 miles) from Peshawar, the capital of North West Frontier Province.

Another security official also confirmed the crash and casualties and said, "detailed investigations are being carried out."