Mindjiyawa Bakary, governor of Cameroon’s Far North region, said that the attack took place at around 0900 GMT in a crowded market in Mora.
"There were two simultaneous explosions," about 15 kilometers [nine miles] from Mora, Peter Migne, an administrative official, told Anadolu Agency.
Two suicide bombers are among the 20 dead, Migne said.
Bakary said that the death toll may rise as several people were seriously injured.
No group has claimed responsibility for the attack but such assaults have generally been attributed to Boko Haram.
Less than two weeks ago a female suicide bomber blew herself up in Cameroon's northern city of Nguetchewe near the Nigerian border, killing at least 11 people.
More than 1,100 civilians and security force members have been killed in attacks attributed to Boko Haram in the Far North since 2013, according to Communication Minister Issa Tchiroma Bakary.
Cameroon has reinforced its military presence along its border with Nigeria, trying to repel the Nigerian militant group with the help of the local population.