Suicide attacks in the central Iraqi city of Baquba have killed at least 31 people and injured dozens more.
Two car bombs exploded within minutes of each other near government buildings in the capital of Diyala province, 60km (40 miles) north of Baghdad.
A later third blast targeted the city's main hospital, where victims of the first attacks were being treated.
The attacks come just days before parliamentary elections, the third since the US-led invasion in 2003.
Nearly a million military and police personnel have been placed on the highest alert ahead of Sunday's polls, defence officials have told the BBC, amid fears the country could slide back into sectarian conflict.
Baquba, a predominantly Sunni Arab city, has been the scene of frequent fighting between insurgents and US-led troops since Saddam Hussein was ousted.
DEADLIEST ATTACKS SINCE 2003
Mar 2004: 171 killed in bombings in Baghdad and Karbala
Nov 2006: 202 killed in multiple blasts in Baghdad
Mar 2007: 152 killed in truck bombing in Talafar
Apr 2007: 191 killed in car bombings in Baghdad
Aug 2007: More than 500 killed in attacks on villages near Sinjar
August 2009: 95 killed in truck bombs in Baghdad
Oct 2009: 155 killed in twin truck bomb attacks in Baghdad
Dec 2009: At least 127 killed in a series of car bombs in Baghdad
Source: News agencies, BBC
In the first attack, a driver detonated the explosives inside his car at a checkpoint near a government housing office and a police station at about 0930 (0630 GMT) on Wednesday, police said.
Within minutes, another car bomb exploded outside the headquarters of the provincial council in the city, they added.
A third suicide bomber, this time on foot, later blew himself up at the gate of the main hospital as the casualties from the earlier blasts arrived, and during a visit by the provincial police chief, Maj Gen Abdul Hussein al-Shimmari.
"The suicide attacker was wearing a police uniform, with the rank of lieutenant," Ali Mohammed, a wounded policeman, told the Reuters news agency.
Most of the victims are said to have come from the hospital bombing. Several of Gen Shimmari's bodyguards were among the injured.
The BBC's Gabriel Gatehouse in Baghdad says the bombings, the deadliest for nearly a month, will confirm the fears of many who have been expecting some sort of attack as polling day nears.
The bombings in Baquba were the deadliest for nearly a month
The vote is seen as a pivotal moment in Iraq as the US prepares to withdraw large numbers of troops by the middle of the year, our correspondent says.
Iraq's police and military are preparing to mount a vast nationwide security operation to try to prevent attacks before Sunday, he adds.
"We have placed all our security services on the highest state of alert - more than 300,000 in the army, and between 500,000 and 600,000 in the police," Gen Mohammed al-Askari, an adviser to the Iraqi ministry of defence, told BBC Arabic.
There have been angry protests by both Sunni and Shia Arab groups ahead of the election, with Sunnis complaining they are being discriminated against.
In January, a Shia-dominated parliamentary committee tasked with vetting candidates for suspected ties to Saddam Hussein's Baath Party banned hundreds of mostly Sunni candidates from standing, including the head of the National Dialogue Front, Saleh al-Mutlaq.
A court overturned the bans last month, saying the candidates could stand on the condition that their cases were examined after the election. This ruling, however, was later reversed.
Correspondents say it is far from certain that any single group will win enough votes to form a government, prompting fears that relations between Sunnis and Shia will deteriorate even further.
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