A number of car bomb attacks have killed at least 24 people in Iraq's holy city of Karbala and Baghdad.
Sunni insurgents are usually accused of attacking Shia sites
A bomb near the provincial government in Karbala killed at least 15 people. In Baghdad, two bombs killed at least nine people, mostly soldiers.
Baghdad police also said they had found the bullet-riddled bodies of 43 men killed in apparent sectarian attacks.
It comes as Prime Minister-designate Nouri Maliki continues efforts to form a cabinet, months after elections.
Rush hour attack
In Baghdad, the first explosion at 0900 (0500 GMT) targeted an army patrol in the city's Adhamiya district. At least 15 people were injured, including civilians.
A second blast - apparently aimed at a police patrol - followed immediately afterwards, killing one civilian and wounding five.
The Karbala device went off at about 0915 (0515 GMT) as employees returned to work after the weekend.
Police at first said the bomb had killed 21 people and injured more than 50, but hospital reports later put the casualty figures at least 15.
Karbala, about 80km (50 miles) south of Baghdad, is home to two of the most important shrines for Shia Muslims and has been often targeted by insurgents.
The BBC's Andrew North, in Baghdad, says certain groups within the Sunni-led insurgency are widely thought to be running a deliberate campaign of attacking Shia religious sites.
It is feared the Karbala attack is aimed at provoking further communal violence between Iraq's Shia and its minority Sunni Arab community, says our correspondent.
Most of the bodies found recently are suspected to have been murdered in the spate of violence that began after a major Shia shrine in Samarra was bombed in February.
All the bodies discovered in the past 24 hours belonged to men who were "handcuffed and shot in the head" , according to an interior ministry official quoted by AFP news agency.
Twenty-eight were found in Baghdad's western Kharkh area, while another 15 were recovered from the eastern Rusafa district, the unnamed official told AFP.
Elsewhere, an Italian soldier has died from his injuries gained in a blast last month in the southern city of Nasiriya, bringing to five the number of foreign soldiers killed in the 27 April attack.
In the southern city of Basra, British and Iraqi forces are looking into how events unfolded when troops clashed with locals after a UK helicopter crashed on Saturday.
Calm has been restored following the unrest, during which Iraqi police said five locals were shot dead.
Elections were held five months ago and delays in forming a government have fuelled the mainly Sunni Muslim insurgency, amid growing sectarian violence between Sunnis and their Shia Muslim compatriots.
Mr Maliki has until 21 May to install his cabinet, but wrangling over ministerial portfolios has held up the process.