Helicopter gunships targeted militant positions in Pakistan's North West Frontier Province after a temporary truce to quell fighting in Swat Valley collapsed.
Officials say Islamic militants fired at Pakistani helicopters and torched a police station overnight, prompting security forces to retaliate. The North West Frontier Province Home Secretary, Badshah Gul Wazir, told local media that as many as 18 militants were killing during the latest round of fighting.
On Monday, militants called for a cessation of hostilities to collect their dead after three days of deadly battles.
Swat Valley has seen a surge in militant activity since cleric Maulana Fazlullah launched an illegal FM radio station, urging a holy war against the government.
Around 2500 troops were sent to Swat last week to counter the Islamists. A day later some 30 people died - mostly Pakistani soldiers - in a bomb attack against a military vehicle.
Some information for this report was provided by AFP, AP and Reuters.