There have also been reports that fighters were stopping people from leaving some areas.
"We have around 135,000 people who have left their homes there," said Habibullah Khan, the additional chief secretary for the Federally Administered Tribal Areas.
Rising death toll
"We have directed officials in adjoining districts to provide shelter, food and health care to the migrating families. We are setting up more camps to help these people just like refugees."
More than 460 suspected fighters and 22 army troops, have died since Pakistani forces started military operations in Bajaur a week ago, officials say.
Abdul Rehman Malik, the head of Pakistan's interior ministry, said intelligence sources claim that about 3,000 fighters remain in the northwestern region of Bajaur. He also said they included Pakistanis, Afghans and Central Asians.
Malik also vowed to "wipe out" the fighters.
Witnesses said that thousands of families had arrived in Shabqadar, a small town adjoining the tribal belt. Local residents and welfare groups were raising funds and cooking food for them, they said.
Local residents in the Mammoond area of Bajaur have said that pro-Taliban fighters had banned people from migrating, saying that if they left the area it would be a sign of defeat.
'Taliban leader killed'
Pakistani authorities are investigating whether a senior Taliban leader was among nine suspected fighters killed near the Afghan border, officials have said..
According to Mohammed Khan, a government official, helicopter gunships fired on the group near Khar, the main town in Bajur on Thursday during a military offensive.
Khan said the targeted vehicles had previously been in the use of Maulvi Faqir Mohammed, who is believed to be an associate of Ayman al-Zawahri, al-Qaeda's second-in-command
However, late on Thursday, Faqir Mohammed's spokesman claimed he had escaped the attack.