Islamist militants have claimed responsibility for a Cairo bomb attack that killed at least three policemen and injured several others. Officials say that one of those killed was a key witness in the trial of ousted Islamist President Mohamed Morsi.

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The attack killed two police lieutenant colonels and a recruit, according to Egypt’s Foreign Ministry. The explosion injured five more policemen and one civilian, state television reported.



The blast was caused by an improvised explosive device that was planted on a tree near the back entrance of the ministry building, located on the back of the Nile in the Boulaq Abu Eila neighborhood, local media reported. The bomb allegedly targeted a police checkpoint near the entrance, security sources told AP.



One of the officers killed in the attack – Lieutenant Colonel Mohamed Mahmoud Abu Sareeaa – was a key witness in the trial of former president and Muslim Brotherhood leader Mohammed Morsi, related to a 2011 mass prison break, court and security sources told Reuters. However, it is not clear whether the policeman was the target.



The Sinai-based jihadist group Ajnad Misr, or Soldiers of Egypt, claimed responsibility for the attack in a statement on Twitter.



"This new operation shows we can penetrate and reach the vicinity of the Ministry of Foreign Affairs...to destroy the officers of the criminal security agencies and make them taste some of what they have made Muslims taste," said the statement.



Ajnad Misr's attack on the Foreign Ministry was claimed by the group as part of its campaign of “retribution.”



"Vengeance operations being carried out by a blessed group from this proud people will not stop," the group said.

The Sunday attack was the worst in months. The latest significant attack in Cairo was performed on June 30 by the same group, when two policemen were killed trying to defuse explosive devices.



Ajnad Misr is known to have carried out 16 attacks, killing at least six police officers and a civilian since 2013, according to the Tahrir Institute for Middle East Policy. The group does not target civilians, and instead directs its hostilities toward state actors. Ajnad Misr has been the most active terrorist group operating in Egypt outside of the Sinai Peninsula, mainly in the area of Greater Cairo.



The group has said that the Cairo bombings were carried out as revenge for the more than 1,400 pro-Morsi protesters that have been killed in street clashes with police.



Explosions targeting police sites and personnel have intensified over the past year, following the ouster of Islamist President Mohamed Morsi in 2013 in an army coup d’état. Morsi is currently in jail and under investigation over inciting violence.



The new military-backed government, headed by the incumbent President Abdel Fattah al-Sisi, proclaimed the Muslim Brotherhood a terrorist group in December. Most Islamist top leaders and supporters have been killed or imprisoned following the coup. In April, 683 Muslim Brotherhood supporters loyal to Morsi were sentenced to death in a widely criticized mass trial. All but 110 were tried in absentia.