The journalist visited the home of ex-transport minister Alain Edgard Mebe Ngo'o on Saturday, the day after the politician left the top job.
"After reporting to a guard at the entrance of the residence, the journalist was arrested by the minister's police service, then undressed, violently slapped, put inside a cage for dogs and sprayed with water," the NGO Reporters Without Borders (RSF) said.
Accused of espionage, he was interrogated for several hours, the statement added.
Editor Haman Mana said on Monday that the newspaper reserved the right to take legal action.
The National Union of Journalists of Cameroon "condemned with the utmost energy this heinous act".
The country is ranked 130 out of 180 in RSF's World Press Freedom Index of 2017.