Fighters with so-called Islamic State are likely using villagers from areas around Mosul as human shields, a spokeswoman for the UN human rights office has said.
Citing "corroborated information" from the area, Ravina Shamdasani said that IS had abducted 550 families from villages around Mosul and are holding them close to IS locations in the Iraqi city.
She said the UN human rights office was also investigating reports that IS fighters had killed 40 civilians in one village.
In the purported recording al-Baghdadi said he is "confident of victory" and calls on the people of Mosul to fight the "enemies of God".
Iraqi general in charge of the advance hailed the 'significant' capture of the state TV station.
Iraq's prime minister has warned so-called Islamic State to "surrender or die" as government troops close in on Mosul.