Pakistani security forces clashed with pro-Taliban militants in the Bajaur tribal district, killing up to 25 of the militants, officials said on Thursday.
The fighting broke out late Wednesday when scores of militants attacked a check post in Bajaur's Loi Sam area located close to the Afghan border, reported dpa.
"Initial reports say at least 25 militants have been killed in the retaliatory action," a senior security official said on condition of anonymity.
The clash continued on Thursday as the military provided aerial and artillery support to the ground forces to fight the militants entrenched in their mountain hideouts.
The rebels claimed they had surrounded some 100 military and paramilitary troops in the same area, the Urdu-language Aaj news channel reported. The claim could not be officially confirmed.
Meanwhile, suspected Islamist militants targeted a security convoy with a remote-controlled explosive device, killing two paramilitary soldiers and wounding three others.
The attack came near Bajaur's main town of Khar, according to the official.
Pakistan's tribal districts are regarded as safe havens for al-Qaeda and Taliban elements who frequently infiltrate into Afghanistan to strike coalition troops fighting the US-led war on terrorism.
International pressure is mounting on Islamabad to clamp down on the incursions which, according to some estimates, have increased by around 40 per cent since March when Pakistan's new government launched peace talks with the militants.
After a brief lull, militant violence has resurged in the region, particularly after clashes between government troops and Islamist rebels in the picturesque north-western valley of Swat.
Nine militants, including one of their top leaders, were killed and many were injured in a search and cordon operation in the Kabal sub-district of Swat on Wednesday. Two more died when a bomb they were trying to plant in a girls' school went off prematurely.