A suicide bomber killed five policemen in Iraq's main northern city of Mosul on Thursday, one of a series of attacks around the country that claimed a total of 12 lives, police said.
Most of the attacks came in Al-Qaeda strongholds as Iraqi and US commanders warned that a persistent political vacuum nearly four months after an inconclusive general election risked fanning a new upsurge in violence.
The bomber walked up to a checkpoint in the Shifa neighbourhood in the overwhelmingly Sunni Arab area west of Mosul and blew himself up, killing four officers and wounding four, police said.
Medics confirmed the casualty toll, adding that two of the wounded were in a critical condition.
On Wednesday night, gunmen killed three policemen at another checkpoint in the west of the city, police said.
The gunmen struck at around 10:00 pm (1900 GMT) in a neighbourhood inhabited by economists, most of them government employees.
The regime of now executed dictator Saddam Hussein provided dedicated housing estates for key professional groups.
West of Mosul, in the town of Tal Afar, security forces thwarted an attempted suicide bombing on Thursday morning, police said.
The would-be bomber tried to blow up his car in a livestock market in the town, which has a large Shiite Turkmen community.
But officers spotted him, and shot and killed him before he could detonate his payload.
Nineveh province, which has its headquarters in Mosul, has remained a hotbed of insurgent activity even as levels of political violence have fallen off in much of the rest of the country.
Nineveh is split between Sunni Arab and Kurdish communities who are bitterly divided over the ambitions of Kurdish leaders to incorporate large chunks of the province into their autonomous region in the north. It also has Assyrian, Shabak, Turkmen and Yazidi minorities.
Al-Qaeda has exploited the ethnic and confessional differences to make the province one its enduring strongholds in Iraq.
In Diyala province, another ethnically mixed jihadist stronghold further south, militants killed two anti-Qaeda militiamen, security officials said.
Four armed assailants stormed the home of the militiamen in the province, just north of Baghdad, in the early hours of the morning and seized the two brothers aged 20 and 22, operations command in the provincial capital Baquba said.
The two men's bodies were found a few hours later dumped by the roadside in the desert Udhaim area in the west of the province, riddled with bullets, blindfold and with their arms bound.
There has been a spate attacks in Diyala against members of the Sahwa (Awakening) militia, an anti-Qaeda force formed under US military sponsorship from 2006 from Sunni Arab tribes and insurgent groups opposed to the jihadists.
The province is an ethnic mosaic of Shiite and Sunni Arabs, and Shiite Kurds and Turkmen, and Al-Qaeda has profited from communal animosities to establish a major base for its operations.
On Tuesday, a sticky bomb killed local Sahwa commander Sheikh Raad al-Tami when he got in his car in the Diyala town of Buhruz, south of the provincial capital.
In the capital, two roadside bombs targeting a police patrol in the Palestine Street neighbourhood killed two police and wounded eight people, four of them police, the interior ministry said.
US and Iraqi officials had warned of the dangers of an upsurge of violence if negotiations on forming a new governing coalition after the March 7 election dragged on too long, giving insurgent groups an opportunity to further destabilise the country.
Government figures showed that 337 people were killed as a result of violence in May, the fourth time this year that the overall death toll has been higher than in the corresponding month of 2009.