The two buses, carrying around 100 passengers, collided in the town of Khanpur, some 800 kilometres (497 miles) south of the capital Islamabad.
"At least 27 people have been killed in the accident and 50 others were wounded," local government official Zafar Iqbal told AFP.
Rescue workers were attempting to pull people out of the wreckage, with fears that the death toll could rise, Iqbal said.
Pakistan has one of the world's worst records for fatal traffic accidents, blamed on poor roads, badly maintained vehicles and reckless driving.
Election Results for Lok Sabha Election 2019 will be out on May 23. Get the latest election news and live updates on ndtv.com/elections. Catch all the action on NDTV Live. Like us on Facebook or follow us on Twitter and Instagram for news updates from each of the 543 parliamentary seats for the election 2019