A wave of bombings and shootings swept Iraq on Wednesday, killing at least 50 people and raising fears that al-Qaeda had launched a promised new offensive. In a Web posting on September 15, the Islamic State of Iraq, an al-Qaeda front group, announced a new offensive for the ongoing Islamic holy month of Ramadan in memory of Abu Musab al-Zarqawi, the founder of al-Qaeda in Iraq who was killed last year in a U.S. air strike. The statement said the Islamic State would hunt down tribal sheiks and officials who cooperate with the Americans. U.S. military spokesman Maj. Gen. Kevin Bergner acknowledged Wednesday that “we have seen an upturn in levels of violence in the last few days” and said the military would step up efforts “to keep pressure on extremist networks.” “This is a specific period of time … that the insurgents will try to increase the levels of violence,” he said, referring to Ramadan. Bergner confirmed the raid on the Iraqi military academy at Rustamiyah, saying it was carried out by Iraqi soldiers with American advisers. Defense Ministry spokesman Maj. Gen. Mohammed al-Askari said those detained faced charges of murder, kidnapping and corruption. Al-Maliki said his country had reduced sectarian killings and brought stability to some regions, such as Anbar province in the west. He said thousands of displaced families have been able to return home. However, an official of the International Organization for Migration told reporters in Geneva that an estimated 60,000 Iraqis were fleeing their homes every month to escape sectarian violence, intimidation and economic deprivation.