North West region governor Adolphe Lele Lafrique told Reuters a manhunt had been launched for the "terrorists" behind the massacre. "Investigations are on, and we will issue a statement on this later today," he added.
A witness said the attackers arrived in vehicles late on Sunday, ordered people onto the floor with accusations of failing to back local separatists, and opened fire as some obeyed while others ran.
The Ambazonia Defense Forces (ADF), the main separatist group in the English-speaking region which has been fighting since 2017 to protest alleged marginalization by the majority French-speaking government, denied responsibility.
The witness said men in military uniforms arrived in two vehicles to storm Nacho Junction, where restaurants, bars and shops are located, at around 7:30 p.m. (1830 GMT).
They shot at people indiscriminately, the witness said, before taking off.
"There is the possibility that it could be revenge killing," ADF spokesperson Lucas Asu said, suggesting the attackers could have been disguised as separatist fighters.
More than 6,000 people have been killed in Cameroon's English-speaking regions since conflict erupted in 2017 after protests were violently suppressed.
Earlier this month, human rights group Amnesty International slammed government troops, militias and separatists for killings, rapes, torture, burning of houses and other atrocities in Cameroon's English-speaking regions.
It said those who speak out were being threatened and detained.