Dang Wangi OCPD Asst Comm Mohamad Zainal Abdullah said they were alerted about the case around 4.15am on Saturday (July 31).
"We received a call about the incident and dispatched personnel to the scene.
"Investigations revealed the body was that of a 28-year-old man," he said in a statement on Saturday.
He said based on initial investigations, police believed the man was murdered as bruises were found on his wrists and forehead.
"Further investigations revealed the unit was rented under the name of one of the victims' friends.
"We have arrested a 20-year-old suspect who we believe can assist with further investigations," he said, adding that the motive of the murder has yet to be established.
ACP Mohamad Zainal said the body has been sent to Hospital Kuala Lumpur for post-mortem.
"We have classified the case as murder under Section 302 of the Penal Code," he said, urging anyone with information on the case to come forward.
Those with information can contact the Dang Wangi police headquarters at 03-2600 2222 or the Kuala Lumpur police hotline at 03-2115 9999.