The Nigerian Islamist group Boko Haram has posted a video on YouTube claiming responsibility for the bombing last week of a major newspaper's offices.
Seven people died in the attacks on ThisDay in the capital, Abuja, and the northern city of Kaduna on Thursday.
A voice-over on the film, which shows the suicide blast in Abuja, threatens further attacks against media groups for committing crimes against Islam.
Boko Haram says it wants to establish Islamic law in Nigeria.
Over the last 20 months its fighters have targeted government institutions, churches, bars and schools across northern Nigeria.
Last year, the group also attacked the UN headquarters in the capital, Abuja.
Residents in the north-eastern city of Maiduguri, where the militants have their headquarters, named the group Boko Haram, which means "Western education is forbidden".
In the nearly 18-minute video, Boko Haram said that ThisDay newspaper was attacked in relation to the Miss World beauty pageant held in Kaduna in November 2002.
Riots were sparked after an article mentioning the beauty contest and the Prophet Muhammad was considered blasphemous.
"We attacked ThisDay because we will never forget or forgive anyone who abused our prophet," the video says.
It went on to say its fighters would target several other Nigerian newspapers and some foreign broadcasters, and warned others that they were "on the verge of joining this list if they are not careful".
Towards the end of the recording, Boko Haram also claimed responsibility for attacks on universities in the northern city of Kano and north-eastern Gombe state in the last week.
It said they would continue to attack universities as "the government has now resorted to arresting our wives and children and also demolishing our houses".
"That is why we have also resolved to start attacking government schools, especially, tertiary ones," the video's narrator said.
Boko Haram first came to prominence in 2009 when hundreds of its followers were killed as they attacked police stations in Maiduguri.
Its founder, Mohammed Yusuf, was arrested but died in police custody.
In 2010 the group started to stage drive-by shootings on government targets in revenge for his killing.
Their attacks have killed hundreds of civilians, both Muslim and Christian.