At least 10 Pakistani soldiers and 23 anti-state fighters have been killed in a gunfight in the northwestern tribal area of Khyber Agency, military officials say.
The clash took place in the Tirah Valley of the tribal district, which borders Afghanistan, early on Friday morning.
Three soldiers were also wounded in the clashes, an official with the public relations wing of the Pakistani military told Al Jazeera, on condition of anonymity.
Khyber administrator Mutahir Zeb Khan confirmed that the gunfight had taken place to the AFP news agency, saying that fighters associated with the Lashkar-e-Islam group "attacked our outpost and a gunfight erupted".
The fighters attacked three hill-top checkpoints that had recently been set up by the Pakistani military, a security official told the Reuters news agency.
Lashkar-e-Islam, which is led by warlord Mangal Bagh, is said to be linked to Pakistani Taliban fighters and criminal gangs.
It was not possible to independently verify the official account of the incident as access to the area is restricted by the military.
Khyber was the site of an army operation last year, which prompted about 18,000 people to flee their homes, seeking refuge in camps and with relatives.
The Tirah Valley has been the site of continued violence over the last several years, with both military operations and fighting between rival groups taking place regularly.
Khyber is one of the main land supply routes to Afghanistan for US-led NATO forces. The route has been suspended by Pakistan since a cross-border clash between NATO and Pakistani troops left 24 Pakistani soldiers in November last year.
Intelligence official killed
In a separate incident on Friday, gunmen shot and killed an intelligence official in the northwestern city of Peshawar, capital of Khyber Pakhtunkhwa province, police said.
Bashir Khan, an Intelligence Bureau inspector, was on his way to work on his motorcycle when gunmen also riding a motorbike shot him, senior police official Tahir Ayub told AFP.
Khan, 38, died at the scene, he added.
While it was not immediately clear who shot Khan, Pakistani Taliban fighters have attacked and killed intelligence officials in the area in the past.
Pakistan's seven tribal districts near the Afghan border are strongholds for local armed groups, many of which are allied to the Tehreek-e-Taliban Pakistan, or Pakistani Taliban, which is also based in these districts.
The military campaign along the entire border region and across several tribal agencies involves more than 100,000 Pakistani troops, but it has effectively reached a stalemate in many areas.