(BBC) About 1,000 Pakistani soldiers backed by helicopters have clashed for a second day with Islamic militants in South Waziristan.
The troops are hunting militant leader Abdullah Mehsud, who is wanted for kidnapping two Chinese engineers last week, one of whom was killed.
The assault is taking place on suspected hideouts around the village of Spinkay Raghzay.
Pakistan began major operations against militants in the region in March.
The BBC’s Haroon Rashid in Peshawar says there have been no casualty reports so far.
Local militant commander, Haji Umer, told the BBC his forces had restarted armed operations after the collapse of month-long negotiations with the government.
Alam Gul Bitani, a resident of the nearby village of Jandola, told the Associated Press that dozens of families were streaming into his village to escape the army operation.
“We could hear artillery fire the whole night,” he said.
The operation followed an ambush on a military convoy on Tuesday that left five soldiers and a number of attackers dead.
The convoy of a dozen vehicles was said to have been attacked by masked men with grenades and rockets.
Pakistan vowed to track down Mehsud after one of two Chinese hostages died in a rescue attempt by Pakistani forces last week.
Five kidnappers were killed. Mehsud directed the kidnapping from another location.
Analysts say the kidnapping was an attempt to secure the release of al-Qaeda militants held during army operations in South Waziristan.