Police officials said the collision took place because of low visibility due to dense fog near Kandhkot bypass, in which six people were reported dead on the spot while 22 were injured, of which six are in critical condition.
One of the buses that collided was en route from Karachi to DG Khan, while the other was going to Karachi from Kohat.
The injured were shifted to Civil Hospital from where six critically wounded persons were referred to hospital in Rahim Yar Khan.
In Gujrat district, according to details, a van collided with a trailer at the Jalalpur Hattan Road on Sunday night, killing two women and a minor girl.
At least eight persons were also wounded in the accident and were shifted to Aziz Bhatti Shaheed Hospital by the rescue workers.
The deceased were identified as Shamim, Sumaira and Noor Fatima. The rescue sources said the dead and injured came to Gujrat from Sialkot to attend a marriage ceremony.