Key border crossings between Pakistan and Afghanistan were closed on Sunday after fierce clashes erupted overnight following Taliban accusations that Islamabad had carried out air strikes this week, officials said.
Officials from both sides of the border told AFP that crossings at Torkham, which connects Pakistan's Khyber Pakhtunkhwa province with Nangarhar in Afghanistan, and Chaman, more than 800 kilometres (500 miles) to the southwest, were closed.
A senior Pakistani official in Torkham told AFP extra paramilitary troops had been sent to the area, which sits on the border between Kabul and Islamabad.
"The Torkham border has been completely closed for pedestrian movement and trade," said the official, who spoke on condition of anonymity because he was not authorised to speak to the media.
"Security forces have also pulled out all civilian staff posted at the border, so they are not harmed in case of further firing," he said.
Another Pakistani border official at Chaman, which links Balochistan province with Kandahar, the birthplace of the Afghan Taliban, said the crossing was "sealed".
Other Pakistani officials said there had been clashes using heavy weapons in at least four border districts, but there had been no casualties on their side.
TTP militants have intensified their campaign of violence against Pakistani security forces in the mountainous areas bordering Afghanistan in recent months.
More than 500 people, including 311 troops and 73 policemen, have been killed in attacks between January and September 15, a military spokesman said on Friday.
A UN report this year said the TTP "receive substantial logistical and operational support from the de facto authorities", referring to the Taliban government in Kabul.
Pakistani Defence Minister Khawaja Muhammad Asif told parliament on Thursday that several efforts to convince the Afghan Taliban to stop backing the TTP had failed.
"Enough is enough," he said. "The Pakistani government and army's patience has run out."