Iraq today suffered one of its worst days of violence this year as insurgents struck government buildings in Baghdad, killing at least 112 people and injuring up to 197.

The explosions happened within minutes of each other, with police saying there could have been as many as four or five. Insurgents, who included suicide bombers, detonated powerful explosives near the labour ministry building, a court complex near the Iraqi-protected Green Zone and the new site of the finance ministry after its previous building was destroyed in attacks in August.

An interior ministry official said at least 99 people were killed and 192 injured in those three assaults.

"We had entered a shop seconds before the blast, the ceiling caved in on us, and we lost consciousness. Then I heard screams and sirens all around," Mohammed Abdul Ridha, one of the 197 wounded in the blasts, told Reuters.

About an hour before those blasts, a suicide car bomber struck a police patrol in the mostly Sunni district of Dora in southern Baghdad, killing at least three police officers and one civilian, and injuring five people.

The explosions underlined the precarious nature of security in Baghdad ahead of an auction of oilfield contracts at the weekend and with elections due in February. Iraqi and US military officials fear that insurgents will step up their attacks to weaken the authority of Nouri al-Maliki, the prime minister, ahead of elections that are meant to showcase Iraq's return to political stability.

Although violence has declined sharply recently - the health ministry last month reported the lowest monthly death toll of civilians in six and a half years - insurgents continue to target Iraqi security forces and civilians.

Today's attacks are the deadliest in Baghdad since late October, when at least 155 people died in car bomb attacks outside municipal offices.

That attack, and a similar bombing in August, marked a change of tactics. Rather than frequent small-scale attacks against soft targets, such as markets or mosques, insurgent groups have recently carried out far more spectacular and lethal attacks against heavily defended government buildings.

Iraqi authorities blamed the October attacks on loyalists to Saddam Hussein's banned Ba'athist party, and paraded on national television three suspects who gave what officials termed confessions. But there are questions over whether Iraqi leaders are seeking to divert attention from a possible resurgence of Sunni insurgency led by al-Qaida in Iraq. A rise in violence could undermine the government's claims that it can provide security without the help of US troops.

On Sunday, Iraqi MPs approved plans to hold parliamentary elections early next year, seen as an important step towards political reconciliation and easing the withdrawal of US troops. The vote, during an emergency session, followed marathon talks to break an impasse over balloting provisions that would satisfy the country's rival groups.

In an attack yesterday, at least eight people died in an explosion outside a primary school in a Shia district of Baghdad yesterday. Six children, aged between six and 12, were among the dead.