The accused allegedly killed his wife, Zainab, 37, and her daughter, Petra, in their bedroom but dragged their lifeless bodies to the kitchen.
The 53-year-old suspect was alleged to have killed the victims in the bedroom at their Banana Island Lagos residence last Thursday but dragged their dead bodies to the kitchen to make it look like it was an accident.
This was the result of the police preliminary investigations into the incident that sparked outrage among Nigerians on social media platforms.
Nielsen, a citizen of Denmark, was arraigned on a two-count charge before the Yaba Magistrate Court, Lagos, but he pleaded not guilty to the charges.
The Magistrate, Mrs. K.B. Ayeye, ordered that the suspect is remanded in Ikoyi Prisons pending advice from the State Director of Public Prosecutions (DPP).
The prosecutor, CSP Effiong Asuquo, told the court that the accused committed the offences on April 5 at his residence at Block 4, Flat 17, Bella Vista Tower, Banana Island, Ikoyi.
He alleged that the Nielsen killed his wife, Zainab, 37, and her daughter, Petra, in the house.
"The accused who was always at loggerheads with his wife had hit her head on the wall several times leading to her death; he also proceeded to poison his daughter. He had dragged their lifeless bodies under the gas to create the impression that they suffocated to death as a result of a gas leakage," Asuquo said.
The offences contravened Sections 223 of the Criminal Law of Lagos State, 2015 which prescribes death sentence for offenders.
The case has been adjourned until May 8 pending DPP's advice.