The deceased were identified as Faizul Islam Chowdhury, 60, of Kanaighat in Sylhet and Zinat Khan, 50, of Mymensingh Sadar upazila and a nurse of Mymensingh Medical College Hospital.
Police said a Mymensingh bound bus plunged into a roadside ditch when its driver lost control over the steering, leaving the two dead on the spot and 10 others injured at 4 am.
During the rescue operation, another truck plunged into the same ditch as its driver lost control over the steering.
Later, another Dhaka-bound bus collided head-on with an oil laden tank lorry injuring 10 more people at the same spot and plunged into the roadside ditch around 10:15 am.
Kotiadi highway police in-charge DM Jahirul Islam said dense fog and slippery road caused the accidents.