At least 30 people were killed and 55 injured when a suicide bomber blew himself up at al Temimi mosque in Baghdad's Kasra area in the evening, reported Xinhua citing an interior ministry source.
Earlier in the day, 15 people, including four soldiers, were killed and eight wounded in separate attacks in Iraq, police said.
In the northern province of Nineveh, four soldiers were killed, including an officer, when some gunmen using assault rifles attacked their checkpoint in Mosul city, some 400 km from Baghdad, a provincial police source said.
In a separate incident, a primary school principal was shot dead by gunmen in front of his house in Mosul, the source said.
Meanwhile, gunmen shot dead a civilian in a village in Mosul, while a police force found unidentified bodies of two young men in eastern part the city, with bullet holes in their heads and chests, the source added.
In Diyala province, three policemen were killed and four wounded when gunmen attacked a checkpoint near the town of Buhruz, some 65 km from Baghdad, a provincial police source anonymously told Xinhua.
Separately, an official of the Sunni endowment office, responsible for running the Sunni mosques, was killed with his wife in a roadside bomb explosion near their car in Kan'an city, some 20 km east of Baquba, the source said.
In addition, a child was killed and four people were wounded when two roadside bombs went off near two houses in the eastern suburb Maqdadiyah city, some 40 km from Baquba, the source added.
In southern Iraq, gunmen shot dead a Sunni imam near his mosque in the town of Abu al-Khasib in southeast of the oil-hub city of Basra, some 550 km from Baghdad, an official said.