"We saw a lot of dead bodies killed by gunshots and some by the roadside that appeared to have been slaughtered" with their throats slit, the driver, who asked to be identified only as Shaibu, told reporters Sunday in Maiduguri, the capital of Borno state.
Shaibu said his terrified passengers wanted to turn back, but "I took the risk ... and said God is in control."
Adamawa state spokesman Ahmad Sajoh said the wedding fatiha, the official Muslim ceremony, had taken place in Firgi village in neighboring Borno state and the groom and guests were driving home to Adamawa when they were attacked.
Last week, suspected extremists attacked a military checkpoint in the same area and witnesses said they killed at least four security force members and made off with army vehicles, weapons and ammunition.
Attacks continue in northeast Nigeria more than five months after the government declared a state of emergency and flooded three states that cover one-sixth of the country with troops and police officers.
They have driven the insurgents from major towns and attacked bush camps aerial bombardments and ground assaults. Hundreds of combatants and civilians, mainly Muslims, have died in recent weeks.
The uprising aimed at installing an Islamic state poses the greatest threat in decades to the cohesion of Nigeria, which is Africa's biggest oil producer and most populous nation of more than 160 million people divided almost equally between the mainly Muslim north and predominantly Christian south.