Iraq's security forces locked down key routes in Baghdad on Wednesday after the country suffered its deadliest violence in two months in the run-up to a landmark Arab summit due next week, according to media reports. The measures came a day after a wave of nationwide gun and bomb attacks killed 50 people and left 255 others wounded on the anniversary of the start of the US-led invasion of Iraq. The closures worsened already choking traffic in Baghdad, which has seen unprecedented levels of security as part of preparations for the first meeting of the 22-nation Arab League to be held in the Iraqi capital in 20 years. The violence rocked 20 towns and cities spanning the northern oil hub of Kirkuk and the Shia shrine city of Karbala, south of Baghdad, from 7 a.m. (0400 GMT), and continued through the day. Parliament speaker Osama al-Nujaifi condemned the "brutal criminal" attacks, and said they were part of efforts by Al-Qaeda to "derail the Arab summit, and keep Iraq feeling the effects of violence and destruction." Following the attacks, the government declared a week of public holidays from March 25 to April 1. Coupled with Kurdish New Year festival Nowruz on Wednesday and the weekly Muslim day of prayer on Friday, much of Iraq will be largely closed until after the summit.