The explosion occurred in the early afternoon on a desert road, about 20km (12 miles) from the city of Samarra, security sources told the BBC.
The explosives-filled vehicle was being escorted from the insurgents’ compound to a main road when it blew up.
The area around the mainly Sunni city of Samarra, in Salah al-Din province, has long been an insurgent stronghold.
The head of the local Sunni pro-government militia, or Sahwa, told the AFP news agency that the insurgents had been filming a propaganda video of the would-be suicide attacker at the time of Monday’s explosion.
Meanwhile, a police officer told the Associated Press that security forces rushed to the area after hearing the sound of the explosion and arrested 12 wounded and another 10 suspected insurgents trying to flee.
In a separate development, the speaker of parliament, Osama al-Nujaifi – Iraq’s most senior Sunni Arab politician – survived an assassination attempt in the northern city of Mosul, officials told AFP.
One of Mr Nujaifi’s bodyguards was wounded when a roadside bomb exploded beside his convoy, police and medics said.
There has been a surge in sectarian violence across Iraq in the past year, reaching levels not seen since 2007.
The United Nations says at least 618 civilians and 115 members of the security forces were killed in attacks last month.
However, its figures do not include casualties resulting from the continuing fighting in Anbar, where Sunni militants linked to al-Qaeda have taken control of parts of the cities of Falluja and Ramadi.