The International Press Institute (IPI), a global network of publishers, editors and leading journalists, condemned in the strongest possible terms today’s bomb attacks on Nigerian newspaper buildings.

A suicide bomber in an explosives-laden car drove into the offices of ThisDay newspaper in Abuja, killing at least six people, while a bomb was thrown at a building housing the offices of The Sun, ThisDay and The Moment in Kaduna, according to the Associated Press and other reports.

IPI called on the Nigerian police and security forces to carry out a thorough investigation into the attacks and ensure that whoever is behind them is prosecuted.

“Our heartfelt condolences go to the families and friends of those who lost their lives today,” said IPI Acting Deputy Director Anthony Mills. “We call on the police to conduct an immediate and thorough investigation that results in the arrest of the masterminds behind this attack. The Nigerian authorities are responsible for ensuring the security of journalists, and ensuring an end to impunity in Nigeria.”

ThisDay Board Chairman Olusegun Adeniyi told the Daily Trust that two people had been confirmed dead while five others were wounded. The Abuja printing plant, one of two such facilities belonging to ThisDay in Nigeria, has been completely obliterated, according to managing director Eniola Bello, who spoke to IPI from Lagos.

The Sun’s chief editor and managing director Tony Onyima told IPI that three casualties had so far been confirmed in Kaduna, a city that has been the site of ethnic violence in the past.  “We have no  clue what the reason was,” he said by phone from Lagos. “For them to have targeted media houses shows that this matter has reached a ridiculous level. We will take steps to protect our staff, and this will not deter us from telling the truth.”

While it is not yet clear who is behind the attacks, the terrorist group Boko Haram last year threatened to go after media for allegedly misrepresenting it in reports. The group claimed responsibility for the October 2011 killing of Zakariyya Isa, a journalist working for the state-run Nigerian Television Authority (NTA), and said he had been “spying” for the government.  In January 2012, Eneche Akogwu of Channels TV was shot while covering the aftermath of a terror attack carried out by Boko Haram in the city of Kano that took the lives of over 170 people, according to news reports.