Three Shiite pilgrims were killed and up to 31 others, including a police chief, were wounded in coordinated bomb attacks targeting Shiite pilgrims in Iraq's eastern province of Diyala on Sunday, a provincial police source said. The attack took place in the morning when a suicide bomber blew up his explosive vest at a procession of Shiite pilgrims in al- Gatoon area in western Baquba, some 65 km northeast of Baghdad, killing three pilgrims and wounding up to seven others, a source from Diyala's operations command told Xinhua on condition of anonymity. In earlier report, the source put the toll at three killed and four injured. Afterwards, a roadside bomb went off near the convoy of Major General Raghib al- Omayri, chief of Diyala's Federal Police Force, who arrived to visit the scene of the earlier suicide bomb attack, wounding him, six of his bodyguards and 17 civilians, the source said. The roadside bomb, apparently, was prepared to cause more casualty among the Iraqi security forces and civilians who were expected to gather at the scene of the first attack, the source added. Shiites in Iraq are marking the 10-day annual Ashura mourning rite, the holiest of the Shiite religious calendar, which marks the death in 680 AD of Imam Hussein, grandson of the Prophet Mohammed. The Shiite mourners usually gather in processions in their towns and cities before they move on foot or buses to the holy shrines in Karbala, some 110 km south of Baghdad. Iraqi and U.S. officials frequently blamed al-Qaida militant group and some insurgent groups for carrying out attacks against Shiite pilgrims who perform communal rituals, killing and wounding hundreds of them in attempts to provoke sectarian strife in the violence-shattered country. Diyala province, which stretches from the eastern edges of Baghdad to the Iranian border east of the country, has long been a stronghold for al-Qaida militants and other insurgent groups since the U.S.-led invasion of Iraq in 2003 despite repeated U.S. and Iraqi military operations against them. 