At least 30 Iraqis were killed and 29 wounded in a suicide attack at a cafe near Baquba.
A suicide bomber blew himself up at the cafe in Balad Ruz town, 35 km north of Baquba in a mixed Shiite-Sunni region in Diyala province north of Baghdad Wednesday.
The attack followed one in southern Baghdad that saw least three more Shiite pilgrims killed and 11 wounded by unidentified gunmen - a continuation of violence against Shiite pilgrims on their way to Karbala to take part in a memorial ceremony marking the martyrdom of Imam Hussein.
The victims were shot in the Sunni-dominated Doura district of southern Baghdad.
The violence came after Iraqi authorities had announced Tuesday that security had been beefed up in and around Karbala in preparation for the ceremony due to begin Friday.
Also in southern Baghdad, a bomb attack on an Iraqi police roadblock killed 12 policemen and 10 civilians, the US military said.
An Iraqi intelligence source said that Iraqi and US security forces had intensified their campaigns against the Islamic State in Iraq, an affiliate of the Al Qaeda terrorist network, in Baghdad, Anbar and Diyala, over the last month.
This has led many movement members to move to Salaheddin province, north of Baghdad, where they have clashed with Iraqi resistance fighters.
The Iraqi INA news agency reported Wednesday that US and Iraqi forces had arrested a leader of an Al Qaeda cell in Makdadiyah, 110 km northeast of Baghdad Tuesday.
The Islamic State in Iraq issued a statement on a website Wednesday denying that one of their leaders had been arrested, after the interior ministry said Tuesday that the movement's second-in- command had been arrested on north of Baghdad over the weekend.
A high-ranking intelligence source said that the Iraqi security services had been receiving more tip-offs from the public to help them track down terrorists.