Four car bombs kill more than 110 people and maim about 200 throughout the centre of the capital

Iraqi rescue workers evacuate a body at the scene of a bomb blast in Baghdad

Iraqi rescue workers evacuate a body at the scene of a bomb blast in Baghdad. Photograph: Ahmad Al-rubaye/AFP/Getty Images

For the third time in four months, coordinated bombers have defeated Baghdad's security and dealt a blow to the Iraqi government's claims to have made the country's streets safer.

Four car bombs early yesterday killed more than 110 people and injured about 200 throughout the centre of the capital in attacks that replicated two days of carnage in mid-August and late-October.

The bombs detonated within minutes near the city's main court house and the public works and finance ministries.

"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," said Mohammed Abdul Ridha, one of the wounded.

The first blast occurred in the southern Baghdad district of Doura about 30 minutes before the other three. It involved a suicide bomber in a car packed with explosives.

In the second, at the court house, a suicide bomber blew up his vehicle in the car park after getting through a checkpoint, police said.

A third bomber blew himself and his car up near a training centre for judges.

Another explosion struck a temporary building used by the finance ministry after its main premises were devastated by a bomb in August. It was unclear whether this blast involved a suicide bomber.

The pattern has become familiar: mass slaughter, with government buildings toppled at will, then a furious reaction from an election-focussed central government, blaming political foes and insurgents.

The prime minister, Nouri al-Maliki, and his senior officials quickly blamed the devastation on senior Ba'athists living in exile in Syria and an alliance of Islamists and militants.

Iraq and Syria have remained at diplomatic loggerheads since the bombings in August. Both countries withdrew their ambassadors after Iraqi officials accused Syria of harbouring enemies who had vowed to direct and fund a bombing campaign in the run-up to a general election, which is scheduled for 6 March.

Iraqi officials have offered only scant support for their accusations. However, they appear to fervently believe that Damascus has at least given implicit consent to a subversive campaign that was allegedly plotted on Syrian soil.

A dossier prepared by Iraq's security forces and shown to Syrian and Turkish intelligence officials, including the Syrian spy chief, Ali Mdouk, in late August, centres on a meeting that allegedly took place on 30 July in the Syrian town of Zabaniyi.

Details of the dossier, which was presented to the Syrians by the chief of intelligence for Iraq's interior ministry, Hussein Kamal, were made available to the Guardian before Tuesday's attack.

It suggests the meeting was penetrated by intelligence agents, who reported that it was chaired by two well-known Ba'athist figures. Also in attendance were former Iraqi army officers and representatives from militant groups who were active in Iraq's Anbar province throughout the blood-soaked years of 2006-07, including Jaish al-Mohammed, the Salaheddin Army and the Islamic Army of Iraq. "They agreed then to topple the government," the report said. "This was the first time these groups had worked closely together. It was a critical event. They elected a leader and made a unified front."

The official Iraqi version of events is that an unlikely co-operative of secular Ba'athists and militants who eschewed any form of government in favour of a return to Islamic law conspired from 30 July to pool their resources and wreak havoc during the pre-election period.

According to a senior Iraqi intelligence official, the original targets had been bridges spanning Baghdad's rivers, rather than government ministries.

"They wanted to attack four bridges on the same day – the first day of Ramadan," the source said. "But they found out we were following them and they changed their plan and their method. For them, it was a case of my enemy's enemy is my friend."

He said the insurgents initially planned to draw from an arsenal of about 2,000 artillery and mortar shells stored in a cache near Baquba, north of Baghdad. "But we found that," he said. "That's why they abandoned the bridge plan. They instead switched to ammonium nitrate bombs hidden in trucks and water tankers."

Iraqi officials have not been forthcoming about the detail of the investigation, relying on two alleged confessions by conspirators on state-run TV, which they hoped would convince a nervous public that they were on top of the perpetrators.

Many Baghdad residents appear to believe the central claim –that al-Qaida-aligned militants are partly responsible. However, their faith in the government to safeguard them from further attacks seems to be diminishing.

Balsem Ahmed, 33, a cultural ministry employee from west Baghdad, said she had taken leave and bunkered down in her home since the last explosions on 25 October. "I had a feeling the terrorists would target my ministry," she said. "I don't want to die or end up handicapped. I doubt these bombs will stop even after the election. No one feels safe any more. I can't trust the Iraqi security forces to protect me. I'm a prisoner in my home."

Some Iraqis are now calling for ministers to resign. "If I was in the place of the defence minister or the interior minister, I would leave my job today," said businessman Sayed Jassem, 45, from Karrada. "How can we trust them if they can't even protect their own institutions?"

Additional reporting by Enas Ibrahim