The speaker of the House of Representatives, Yakubu Dogara, has said the deployment of the armed forces in more than 28 states means the country is effectively under a state of emergency.
The Speaker said it was worrying that the armed forces have virtually taken over routine police work in Nigeria, which is made up of 36 states.
He was speaking at a security event involving lawmakers in the capital, Abuja.
The fear appears real for a country that came out of military rule less than 20 years ago.
Mr Dogara noted the military used to exercise absolute control over government until the restoration of civilian rule in 1999.
His critics will say there are plenty of reasons for the army to be deployed, including an insurgency by Islamist militants in the north-east, a separatist agitation in the south-east, a threat to eject ethnic Igbos from the north and attacks on oil facilities in the Niger Delta.