In the wake of the attack, 43 bodies were found decapitated by the terrorists, and many other farmers were reported missing.
But the UN official said in a statement that: “At least 110 civilians were ruthlessly killed and many others were wounded in this attack.”
“The incident is the most violent direct attack against innocent civilians this year. I call for the perpetrators of this heinous and senseless act to be brought to justice.”
The bloodletting took place in the village of Koshobe near the main city of Maiduguri, with assailants targeting farmers on rice fields.
Borno Governor Babagana Umara Zulum attended the burial on Sunday in the nearby village of Zabarmari of 43 bodies recovered on Saturday, saying the toll could rise after search operations resumed.
The assailants tied up the agricultural workers and slit their throats, according to a pro-government anti-jihadist militia.
The victims were among labourers from Sokoto state in northwestern Nigeria, roughly 1,000 kilometres (600 miles) away, who had travelled to the northeast to find work, it said.
Six were wounded in the attack and eight remained missing as of Saturday.
Mr Kallon, citing “reports that several women may have been kidnapped”, called for their immediate release and return to safety.
Nigerian President Muhammadu Buhari condemned the attack, saying: “The entire country has been wounded by these senseless killings.”
The attack took place as voters went to the polls in long-delayed local elections in Borno State.
The polls had been repeatedly postponed because of an increase in attacks by Boko Haram and a rival dissident faction, ISWAP.
The two groups have been blamed for increasing attacks on loggers, farmers and fishermen whom they accuse of spying for the army and pro-government militias.
AFP