Insurgents have blown up the local offices of Iraqi prime minister Iyad Allawi's political party in Baquba.
Insecurity still plagues Iraq in the run-up to the handover
Earlier, attackers fired grenades at the offices of another party in the city, killing at least three people.
Elsewhere, a car bomb exploded in the city of Irbil injuring a senior Kurdish politician and killing one of his bodyguards.
The attacks come as an interim Iraqi government prepares to take over the running of the country on 30 June.
BBC diplomatic correspondent Jonathan Marcus says the insurgents are doing all they can to derail the new political process.
More than 100 people died in a wave of attacks on Iraqi cities on Thursday.
Mr Allawi and his ministers have said they will adopt tough new security measures when they assume office but they have also predicted an escalation in violence.
"The Iraqi security forces as well as the Iraqi army will be prepared in a week or two to impose the necessary measures to deal with the terrorists and the terrorist activities throughout the country," news agency AFP quoted the interim prime minister as saying.
"We will be backed by the multinational forces which have been assigned by the United Nations to help Iraq," he added, speaking at a power plant north of Baghdad.
In Baquba, reports quoted witnesses as saying gunmen had stormed the local headquarters of Mr Allawi's Iraqi National Accord, setting off a bomb before fleeing.
In the attack on the Supreme Council of the Islamic Revolution in Iraq building in the same city, three party members were killed and two other people wounded.
Reports quoting US and Iraqi officials said six insurgents had been killed in the wake of the attack.
In Irbil, a car bomb was detonated in a busy commercial street near a culture ministry building, killing a security guard and wounding 40 people, including a Kurdish culture minister.
A report quoting the US military said a US soldier was fatally wounded when his patrol was attacked overnight by rocket-propelled grenades in the centre of Baghdad.