The gunmen, armed with AK 47 rifles, stormed the market Monday, heading straight for the group of hunters, Nigerian newspaper the Daily Trust reported Wednesday.
"The attackers audaciously moved straight to the stand of their targets in the market and opened fire ... there was no sign of fear or sympathy," said an observer whose name was not reported.
"[The gunmen] had dropped some notes, warning that selling bush meat is against the teachings of Islam and eating the meat of monkey is haram," or forbidden by Islamic law, he added.
The attack sent the busy marketplace into chaos as customers and traders tried to run for safety, observers said.
No group had claimed responsibility for the attack as of Wednesday, the Daily Trust reported.