According to police and hospital officials on Sunday, the death toll could rise as rescuers were still digging in the rubble of parts of the buildings.
Four policemen were confirmed dead and at least seven more were among the wounded after the first blast, medical staff said.
The blast struck the Bab al-Hadba station in central Mosul just before people began their working day at 6.15am (0215 GMT).
Brigadier Wathiq al-Hamdani, Nineveh province's deputy police chief, told Aljazeera that two civilians had also been killed and that a large number of shops had been damaged.
"These criminals target police patrols as they attempt to maintain security in the city," al-Hamdani said. "But they will never stop us from continuing our work," he added.
But the deputy police chief could not give details about how the attack was carried out. Some locals spoke of a car bomb attack, others of a rocket striking the building or a bomb planted inside it.
Another 15 people were killed and seven wounded just hours later when a bomber blew himself up in a crowd outside an Iraqi army recruitment station base in northwestern Iraq, the US military said.
The attack happened at about 8am (0400 GMT) at a parking lot next to the al-Kisk base, west of the northern city of Mosul, US army Captain Mark Walter told journalists.
A third attack happened at around 2pm (1000 GMT) when a man strapped with explosives blew himself up at a small police station attached to the Medical City hospital on the city's west side, station commander Mohammed Fathi said.
Most of the casualties from the two earlier attacks had been brought to the hospital, one of the largest in Mosul. Fathi could not provide a toll for the third attack.
In another incident on Sunday, Colonel Riyad Abd al-Karim was killed on his way to work, police in the capital said.
The colonel was deputy head of a main police department in Baghdad.
Two more Iraqis were also killed and three others injured when two mortar shells landed on their houses in al-Baladiyat neighbourhood in central Baghdad.