Armed gangs who kidnapped dozens of passengers in an attack on Abuja-Kaduna train are using civilians as human shields, making it difficult for the military to carry out a rescue mission, President Muhammadu Buhari said on Monday accordingto a Reuters report.

Nigeria's state railway company said last month that 168 people were missing following the March 28 attack.

Local media last week showed a video of victims of the kidnap, including a baby recently born to one of the abducted women. Reuters could not verify the video's authenticity.

Buhari said the government, which has been criticised for not doing enough to rescue the passengers, was trying to avoid a "tragic outcome" in any rescue operation.

"They (the kidnappers) are using civilians as human shields, thereby making it difficult to confront them directly," he said in a statement.

"It's a delicate situation ... Any rescue operation that results in the death of any hostage cannot be deemed a success."

Abductions have become almost a daily occurrence in Nigeria, where the armed gangs abduct people for ransom and hide in forests.

The brutal nature of the attacks have increased insecurity fears in a country also grappling with an insurgency in the northeast and rising criminality around the country.