"I can confirm to you that the abducted Chinese workers have been released. They were freed today through a joint operation by the police and other security agents," state police spokesman Sola Collins Adebayo said yesterday.
He said the hostages who were seized on Friday at a quarry outside state capital Lokoja were unharmed, but declined to say if a ransom was paid.
A senior police officer said earlier yesterday that the gunmen had stormed the quarry and engaged the police on guard there in a shootout that left one officer dead and another wounded.
Kogi state has seen a wave of abductions targeting foreigners this year.
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Two weeks ago, two other Chinese nationals were kidnapped in the state, while an American missionary was taken from her school last month.
The missionary, who works in the village of Emiworo where her Free Methodist Church runs a community organisation, was released last week.
State police said they were unaware of any ransom paid for her release.
Foreign nationals have often been kidnapped in Nigeria by local gangs who typically release hostages following a ransom payment.