The attacks took place in Swat, a valley about 160km northwest of the capital, Islamabad.
Local media reports had stated that about 60 people, including children, had died in army raids near the towns of Shangla, Kabal and elsewhere.
Major-General Waheed Arshad, the army spokesman, did not confirm these reports.
Mortars fired
An army statement said fighters on Wednesday fired six mortar rounds at the airport near Mingora, the region's main town, killing two soldiers and injuring five more.
A local police official said at least two more soldiers died when a roadside bomb exploded near their vehicles at the town of Batkhela on Wednesday.
The military has said only that eight soldiers were injured in the blast.
The police official, who spoke on condition of anonymity because he was not authorised to speak to media, said the army had been assigned to flush out fighters from Swat by the middle of December.
Pro-Taliban hub
Swat has been a focus of a wave of pro-Taliban activities since July when government troops were deployed there after the Maulana Fazlullah urged his supporters to wage a "holy war" against the government.
Since then, the fighters have captured a string of villages and towns in Swat.
Although the government has sent even more troops to Swat to curb Fazlullah's activities, it has yet to regain control.
Authorities this week imposed a curfew in Swat and the nearby district of Malakand in an attempt to contain the fighters, who are demanding implementation of Taliban-style Islamic laws.
Fazlullah, who is on the run from authorities, uses an illegal FM radio station to call for support.
The violence in Swat has left scores of fighters and government forces dead.
Pervez Musharraf, the Pakistan president, cited the deteriorating situation to justify the state of emergency he declared on November 3.