Rescuers had to take people to a nearby town for treatment
The morning blast destroyed the market in the small town of Amirli, south of Kirkuk, killing many people instantly and trapping dozens among the rubble.
It was the deadliest single attack in Iraq since April, correspondents say.
It came as 29 people were killed in separate violence, including 22 people who died overnight in Diyala province when a suicide bomber hit a cafe.
The truck bomb struck Amirli on a busy shopping morning, destroying several buildings around the heart of the market, police said.
Rescuers were forced to move injured people to Tuz Khurmato, the nearest major town, some 45km (28 miles) away, and some casualties were said to have died on the way.
Others were taken on to Kirkuk, the largest city in the region, for more intensive treatment.
"I heard the cries of my child, then I heard nothing else until I woke in hospital," housewife Sukaina Abdul Razak told AFP news agency in Kirkuk.
"I don't know the fate of my husband and my family. They were all in the kitchen, but I was in my room."
Correspondents say the market bombing could have been linked to political developments in the region, where a referendum on the status of Kirkuk province is due to take place by the end of this year. Kirkuk lies outside Iraqi Kurdistan but is claimed by many Kurds for their national capital.
Officials in Diyala said the bomber who struck on Friday night targeted a busy cafe used by the Shia Kurdish community.
The small village is close to the border with Iran.
In other violence, police said a family of seven sleeping on a Baghdad roof died when a mortar hit the building.
The dead reportedly included a couple and their four children, aged nine to 17, as well as a relative.
Many Iraqis choose to spend hot summer nights sleeping on the roof of their home because of frequent electricity failures.
The US and British military also confirmed new deaths.
One British soldier died and three others were injured in southern Iraq during a night of heavy fighting in Basra.
The US said nine of its troops have died in recent days, most in Baghdad and two in the western province of Anbar.