Four Catholic nuns who were kidnapped earlier this week at gunpoint in the state of Imo have been released, police said. Imo state police announced on Wednesday that the nuns were released by their abductors the day before. Officials reportedly said the nuns were returned unharmed. They did not disclose if they were returned in exchange for ransom. RELATED: Four nuns kidnapped by gunmen in Nigeria Kidnappings by militant groups and gangs have increased in Nigeria. It has been speculated ransom paid for kidnapped religious leaders has fueled abductions. More about the abduction and religious violence in Nigeria can be found here.