At least eight people have died in two bomb blasts that targeted media offices in the capital of Abuja and the northern city of Kaduna.
The Abuja attack targeted the offices of This Day, an influential daily newspaper seen as supportive of the regime. In Kaduna a bomb went off in a building housing three newspapers - This Day, The Moment and the Daily Sun. All are supportive of the government.
Nobody has claimed responsibility but Islamist terrorist group Boko Haram was suspected.
In Abuja, a suicide bomber ran his car through the gates of the This Day office and detonated a car loaded with explosives. Three people including two security guards died in the attack.
"The suicide bomber came in a jeep and rammed a vehicle into the gate," said Olusogen Adeniyi, chairman of the editorial board. "Two of our security men died, and the obviously suicide bomber died too."
In Kaduna witnesses said a man threw a bomb into the newspaper building, killing at least five.
Nigerian Red Cross spokesman Nwakpa Nwakpa told Reuters at the scene of the Abuja blast: "We have collected three bodies but before we got here people had already been moved."
Police and firefighters rushed to the scene and soldiers cordoned off the area while emergency workers evacuated the injured.
President Goodluck Jonathan condemned the attack as "ignoble, misguided, horrendous and wicked".
The government, he said, would "continue to uphold the constitutional right to freedom of express in general and press freedom in particular".
"Criminal elements bent on instilling fear in the minds of Nigerians and foreigners will not succeed."
No group immediately claimed responsibility for the attacks but the newspapers targeted are seen as supportive of the government, prompting speculation the Islamic sect Boko Haram could be behind the blasts.