The militants were still in control of parts of Buner valley, just 100 km (60 miles) northwest of Islamabad, though troops had secured the main town of Daggar on Wednesday after helicopters dropped troops behind enemy lines.
The ground troops have established links with the soldiers airlifted to Daggar, but heavy fighting was going on elsewhere in the valley, military spokesman Major-General Athar Abbas said.
"The kind of resistance militants are offering shows what are their objectives. Resistance is still continuing," Abbas told a news conference in Rawalpindi, a garrison town adjoining Islamabad.
He said 55-60 militants including some foreigners were killed in fighting in Buner over the last 24 hours, raising the death toll of militants to more than 170 in the region since Sunday.
Security forces switched to Buner on Tuesday after clearing Lower Dir.
In another district of the region, Upper Dir, over 50 militants stormed the headquarters of a paramilitary force early on Friday and kidnapped 10 of them.
Buner, Upper and Lower Dir are part of the North West Frontier Province's Malakand Division, where the government agreed to allow Islamic sharia law in February if militants shunned violence in their stronghold of Swat valley. Swat is also part of Malakand.
But the militants foray into Buner this month sent jitters across Pakistan and caused the United States to worry about the stability of the nuclear-armed nation, which is vital to U.S. efforts to defeat al Qaeda and stabilize Afghanistan.
CIVILIAN EXODUS
Pakistani military officials say troops were securing the Buner valley at a slower pace to avoid civilian losses. Hundreds of families were seen streaming out of the valley, their vehicles laden with belongings, including cattle.
Abbas said security forces have destroyed several explosive-laden "suicide" motorbikes and vehicles parked by the militants in the battlezone to block advances of the forces.
Abbas said militants had also set up checkposts in parts of Swat in violation of the peace pact, prompting speculation that the offensive could be extended to the valley.
NWFP authorities on Friday opened talks with Sufi Mohammad, an influential cleric of the region who has acted as a go-between with the Taliban, in a renewed effort to stop violence.
"Everything is being done to end militancy. Everything is being done for peace," Mian Iftikhar Hussain, the provincial information minister told reporters after talks with Mohammad in Timergara, in Lower Dir.
U.S. officials have urged Pakistan to follow through on this week's offensives in Dir and Buner rather than let the enemy regroup.
Government officials say they were committed to enforcing sharia law in Malakand but militants had to lay down arms.
The State Department said on Thursday the number of people killed in terrorist attacks in Pakistan last year rose by more than 70 percent, despite an overall drop in such violence worldwide.
President Barack Obama on Wednesday praised the Pakistani army's new resolve to fight militants and said it had begun to realize that homegrown militants posed a bigger current threat to the Muslim nation's stability than old rival India.
A U.S. official said on Thursday the United States and Pakistan will likely discuss stepping up U.S. training for Pakistani security forces when President Asif Ali Zardari visits Washington next week.
Zardari and Afghan President Hamid Karzai will meet separately with Obama and then have three-way talks during visits to the White House on May 6 and May 7.
U.S. lawmakers are likely to consider this month giving more than $400 million to train and equip the Pakistani military in counter-insurgency tactics, which U.S. officials say are vital to Islamabad's ability to defeat militants.
A top al Qaeda commander in a message that appeared on Islamist websites on Thursday urged Pakistanis to rise up against their government.
"Muslims in Pakistan, and especially their clerics, should prepare themselves and rise up to perform the duty ... of fighting the Pakistani army and the rest of the apparatus that are the pillars of their tyrannical state," Aby Yahya al-Libi, who is thought to be in Afghanistan and Pakistan, said in an article dated mid-March.
(Additional reporting by Sahar Ahmed; Writing by Zeeshan Haider; Editing by Bill Tarrant)